If you have any questions you want answered, feel free to drop me a note. If you’ve got a question, chances are, there are lots of others out there with the same question. So ask away!
Note: all comments are moderated unless I’ve approved one of your previous comments. Almost everybody gets thrown off by this, but I moderate comments to avoid spammers. The downside of this is that you won’t see your comments post until I’ve had a chance to review and approve them. Sometimes this can take days (sorry!) Thanks for your patience.
Ted's Energy Tips 
Fujitsu heat pump
Hello Ted, I took the opportunity today to upgrade the insulation on the tubing on my 12RLS. I went to my local building store and bought the common black foam pipe insulation normally used on water heater piping and a/c installations. I’m not sure how this will stand up outdoors, but I noticed that the neoprene used by the installers in Dec. has already started to show signs of deterioration.
Sun damage I guess, veining and checking. Anyway I bought the stuff with 3/4″ ID and it fit quite well over the original neoprene and I just taped it with black electrical tape, a pretty neat job if you don’t get too close. I know that there is some kind of vinyl channel that can be used over the insulation but I can see that it wasn’t very practical in my case and would have meant lengthening the line in order to do it. The installers had left about 1/2″ of pipe inside the small cowling where the lines enter the unit. You know all they had to do was remove the cowl and they could have easily have insulated this easily. Hard to get good help these days. I didn’t want to remove the cowl so I just stuffed the area around the connections with white packing foam, which should not be affected by moisture. Well Ted how long I wonder can I expect this insulation to last?
Hey Jack,
I’ve got the softer black insulation on mine also. It’s supposed to be better than the black foam but both weather poorly in my experience – UV kills most rubbers/plastics so whatever you use, it should be protected from direct sunlight. Mine was installed inside a channel that’s like a gutter downspout. I’ve also used the silver foil bubble wrap to protect the foam insulations.
I moved into our 2 story cap code house built in the 40’s. While gutting the house I noticed there is no insulation in the walls, there is some in the “attic” area. Everything was built with sheetrock and plaster over that. There is a knee wall the extends the entire length of the house (about 6 ft wide and 5.5 ft tall) with a small door for access. We have no soffit vents and at sometime a new roof was put on with a ridge vent. There are 2 gable vents 1 on each side of the attic. Wanting to insulate everything what is the best way to go about this. I live in Central PA, so we get a true 4 seasons. I was just planning on insulated the walls with R-13 kraft backed, and R-38 batts on the attic floor. How should I deal with the knee area? Should I insulate the roof rafters, or the walls? Should I be concerned about the ridge vent and not enough ventilation? After reading plenty of sites on insulating these areas (especially the knee area), nobody has a definite answer. If I put insulation on the roof joists (2×6 24″ centers) do I put it against the roof or leave breather space?
This can be a problematic insulation job. Are you planning on doing it yourself or having a professional insulator do the job? Some things are much easier for a DIY than others.
You’re asking the right questions though. You have to be really careful with your construction. I’ve seen a number of problems when people insulated the entrapped area above the knee wall, between the roof of the house and the ceiling of the room below and didn’t leave a ventilation gap under the roof sheathing. One big problem is the ridge vent without soffit vents. This tends to draw air and moisture up from the house rather than outside, which can lead to severe moisture problems. The gable vents will help as long as there’s free air movement from the vents to the ridge.
I’ll point you to some more pointers depending on how you’re planning on approaching it.
I plan on doing this myself, that shouldn’t be an issue. I would like to have the knee area as conditioned space, so I was planning on running the “channel vents” under the roof and insulating that way. I would then put some sort of panel board up. Granted there are no soffit vents to fully utilize these, but I figured it would keep the hot air vented into the attic, and insulation away from the roof. Since the knee area has no venting at all, should I be concerned or is this basically like a rather large closet now? The gable vents in the attic appear to be large enough, and are completely unobstructed (besides a screen).
It can get messy if you’re not very careful. I highly recommend figuring out a way of providing continuous soffit vents so that you’re providing fresh air flushing from soffits up to the ridge vent in the gap between the insulation and roof deck. Without doing that, you’re really risking a roof rot situation.
I’m guessing that the gable vents are in the small top attic, not the kneewall area that you’re describing as a large closet?
I’ve got an article on this very topic. You may also want to review some of the material on the Building Science website. Here’s one such article and there are others that are worth reading. I’d hate to see you spend a lot of effort and end up creating a problem.
Thanks for the info Ted. And yes you are correct the gable vents are in the attic above the knee area. The problem is there is no way to put soffit vents in, the roof joins the wall with no overhang. I’m not sure if it matters much, but the roof is all 1×6 tongue and groove, then the standard felt paper with shingles. The articles you sent are great, I came across them before, but almost all assume you have soffits or an overhang so you can add them. It almost seems like I’m going to have to give up trying to make this a conditioned space, and just insulate the knee wall and floor.
I’ve run into construction which precludes soffit venting, including half of my own home. The most important thing in this case is to do whatever you can to prevent warm, moist air from the inside of your home from coming in contact with that cold roof deck.
This is certainly possible – think about all the older homes without soffit vents. What’s happened in modern homes is that they’ve gotten considerably tighter, so the moisture builds up rather than being flushed out through all the leaky windows and so forth. When that happens, it works its way up through the house and escapes wherever it can, but in much higher concentrations than it did in times past. With your construction, the ridge vent actually helps to suck air from the house into the attic spaces, increasing the likelihood that moisture problems will arise. Because of this, you have to be especially careful.
This is why, for this construction, I greatly prefer spray foam applied directly to the underside of the roof deck. The foam hermetically seals the area so that warm moist air simply cannot come in contact with the cold roof deck. At least if it’s done properly.
Since you’re looking at a DIY solution, you’d be best off with a solution like rigid board foam applied under the roof deck, with a bit of an air gap – about 1″. Even without the soffit vents, the T&G planking used as decking will be somewhat porous, allowing moisture movement out of the space, albeit slowly. So if it were my roof, I’d use at least one layer of 2″ dense foam board (either blue or pink stuff, not the white stuff). Then, I’d seal the joints where the board is in between the rafters, so that air can’t sneak around the edges. If you do that, you can pretty well seal the easily accessible areas of the roof from the attic. It’s time consuming but doable as a DIY if you pay attention to details.
The trick is where you can’t access the roof any more, where it’s hidden by the ceiling section resting on the knee-wall. Unfortunately, that’s also usually where problems arise because the moist air wants to go up through those channels and out the top attic. One solution (which is somewhat heretical, but logical), is to securely block off these areas using more of the rigid board foam, cut snugly then sealed around the edges. This blocks the moisture from being drawn strongly from the living space up to the top attic. I would still use vent chutes under the roof deck, if you can get them in there, so that there’s a continuous channel with the space in the lower area as described above. Then insulate under this (i.e. behind the sloped ceiling of the room under the attic).
The one case where even this still may fail is if you have a tongue and groove ceiling in the room under the attic. Those ceilings allow so much air movement that it’s virtually impossible to fix them and prevent mold and wood rot in some climates.
I hope this gives some idea of how you might attack the problem. It’s definitely one of the hardest ones in practice to do in a way that won’t blow-up on you in years to come.
Thanks for the advice Ted. I think the best part about your approach is its something I can work on in sections. How would I detail the hip roof sections. That is, I will have several rafter bays that cannot vent to the ridge using your method. Would this even be critical?
Also, regarding the whirlybids. I am thinking these should be removed. If I am venting from the soffit to the ridge, the turbines are fighting the system and should go. Would you agree? Now they do serve a purpose now because there is no ventilation through the cathedral ceiling, but doing your recommendations would fix this problem.
Regarding the ceiling, my wife will not let me. For one, we just finished re-finishing upstairs and our kids are up there. The cathedral ceiling is 3′-8″ wide and is accessible from below and above. Im just going to have to work slowly and chip at it. I do wonder though. The current fiberglass is paper faced, nailed to the rafters and sandwiched/sealed by the drywall. I would think that in these sections, the air sealing would not be as critical as much as it would above and below provided I can remove the fiberglass and preserve the paper. Im thinking a small garden tool would work for this, I forge what its called, but its hand held and has the three bent forks. Agree?
Thanks.
First a caveat to other readers who might misunderstand what you’re saying – energy loss or heat gain is related to the square footage divided by the R-value. So when you insulate most of your attic to R-40 but some sections remain uninsulated, say at R-1, those area let in 40x as much heat for a given square footage. So it’s always best to insulate everything or you’ll lose a disproportionate amount of energy through little uninsulated areas.
On to your real questions…
The sections that don’t/can’t be ventilated are something of a ‘tough luck’ situation. If you look at all the homes that are constructed like this, whether it be roof design or skylights, you’ll find that most have no problems because the ventilation isn’t really doing what people expect it to. In your specific case, you probably rarely get temperatures that are conducive to condensation on the back of the roof deck and when you do, it’s very likely that will be followed by sunshine and higher temperatures that “burn off” any moisture. In those areas, I would continue to treat it like the rest of the roof, with spacers and an air gap, just so that you have a little space in there. OR, you could just completely spray foam those bays because working in those bays might be a pain.
On the whirlybirds – yes. If you insulate under the roof deck, then the whirlybird would work against the rest of the system. The entire attic would need to be sealed and insulated.
On the ceiling – I see! The important thing will be to maintain the continuous ventilation space from below, through that space, up to the top attic. It might be hard to run the board foam through the space, but if you can, go for it! If you do that, you might not have to remove the fiberglass. The total R-value wouldn’t be as good as if it were all poly-iso, but just that 2″ of poly-iso would be adding R-14, so that’s not too bad. You’d compress the fiberglass, losing a little of its R-value when you work the board foam through the space but overall, it would be a net improvement.
My house is pretty efficient, using around 600 gallons of oil a year for heat and hot water (no AC) with pretty standard insulation and sealing. What’s the environmental break even point in terms of the tons of weird chemical foam, rigid foam, fiberglass, and silicone, not to mention replacing the sheetrock and paint, even if I were to halve that amount of oil (which I probably couldn’t)? You’ve done great analyses on other stuff so I was wondering if Ted-san has an opinion on the payback for this foam when you add the environmental cost of the foam versus the saved energy? (Obviously the oil has hidden costs, too, but let’s say you heated with biodiesel. Wouldn’t all the foam be infinitely worse for the environment? Inquiring minds are inquiring.
Hey Dave, that is a valid point – one that often results in heated debate (no pun intended…)
It’s a big “it depends.” For example, the blowing agents used in the two-part home foam blowing kits turn out to be vastly worse than CO2, like orders of magnitude worse. So using those home kits, from a “greenhouse gas” perspective can be pretty ugly. OTOH, the setups that professionals use sometimes run on compressed air, so then it’s a simpler analysis of the ingredients. Since most of these are petrochemical based, you’re definitely using fossil fuels to save fossil fuels. But, if you can take a typical house from 1500 gallons of heating oil to down below 1000 gallons, saving 500+ gallons every year, you quickly reach that break even point. With your home, you might have to switch to a different system, like geothermal, in order to significantly reduce your oil/environmental impact.
(update: see this article about new blowing agents for foams)
One of the reasons I like foam, in spite of the environmental nastiness that’s associated with it, is that it’s essentially a “permanent” solution. You generally don’t have to worry about the next homeowner coming in, pushing it aside, and ruining the energy efficiency of the house. With normal insulation, it’s fairly common to go into the attic and find that people have casually displaced it, leaving uninsulated areas that can easily double the energy loss for the entire attic.
For retrofit walls, green builders generally agree on dense packed cellulose for its high effectiveness and very low environmental impact since it’s essentially 100% recycled newspaper and Borates.
When I was doing energy audits daily, my goal was to help people prioritize remediation projects so that they could focus their efforts where they would make the greatest impact with the least effort. Usually that involved sealing up a few big holes and working on the ducts/HVAC system. The caulking/foaming/reinsulating usually came later in the list. That’s the real value of an energy audit.
Ted,
What’s your opinion about closed-cell foam sprayed on the attic-side of the ceiling to both air-seal and insulate followed by loose-fill and/or batts?
J
Now THAT I approve of. 🙂
It’s an excellent idea. Air sealing manually is a real bear so just spraying an inch or two over everything then using lots of inexpensive insulation (blown cellulose is my preference) on top works really well. And, if you’ve got ducts laying on the attic floor, you can just blow the cellulose over them too to give extra insulation.
Smiles from me. I got two insulation estimates for air-sealing/reinsulating the attic plus foam-sealing the rim-joists (I also need to either cover up or replace jalousie windows in the basement). One estimate was spendy (~$5K) for dense-pack under the attic floor, foam board over the floor, air-seal the cracks, loose-fill the rest, close-cell on the rim joist. The other was slightly less spendy ($3.5K) for an inch of closed-cell on the attic side of the ceiling, replace the batts already there, add loose-fill to R40, and an inch of closed-cell on the rim joists. The only bummer about option #2 is that I have to remove about 15 sheets of plywood from the floor of the attic so they can get in there and since I’m in an owner-built home, there’s about 45 nails per sheet. Thanks again.
That sounds pretty reasonable, except for all those nails! At least it’s ‘only’ 15 sheets of plywood flooring 🙂 One warning when you’re doing that – wear good hearing protectors. I ruined the hearing in out one of my ears when I was doing exactly this removing the sheathing on my garage walls when I deconstructed the garage. I was pounding on these big sheets, removing the nails, and the plywood acted like a big speaker, projecting the noise back at me. After doing one panel which I banged on particularly hard, I got a ringing in my ear that’s never gone away. One moment of indiscretion lead to a lifetime of tinnitus. 😦
Ted –
I found your site last week and there is a wealth of great information here. Thanks!
I recently purchased a 35 yr old house in New Orleans. The attic insulation and sealing is insufficient. The front portion of the house is a 1-1/2 story ranch with a vented attic. There is a rear wing on the house that is a single story, also vented. The HVAC system is located above the rear wing; duct work in-circles the house through the lower crawlspace. The house has soffit vents all around, 2 turbine vents at the top of the crawlspace, 2 turbine vents in the rear wing and ridge vents on top of the crawlspace and the rear wing. Yes I said AND.
I have been through a large number of your articles and I find “Insulating walk-in attics” and “Ultimate attic insulation” to both be of interest to a retrofit project. I have some concerns I hope you can take the time to elaborate on. My roof beams are only 2×6, so I do not have sufficient space to install baffles to vent air from the lower crawlspace to the upper ridge vent and provide ‘adequate’ insulation (to the limitations of 6″ beams). Given this, sealing the attic at the roof line makes a lot of sense. Would you agree?
If I were to take this approach, I should be able to seal the attic using closed cell foam right? I am aware of the roof rot potential issues. However having an older home in a hurricane prone area, I like the structural properties the closed cell foam may provide. My concern is I have talked to many insulating contractors in the area and they all want to use open cell foam. But doing this requires me to pay them to air seal at the ceiling and I would have to adequately vent the attic, which means bridging the lower crawl space to the upper? What are your thoughts on this?
If I were to take this approach, I would remove the existing ceiling insulation, which is a mix of fiberglass batts of different thickness, most of it in bad shape (stepped on, leaked on, etc) and replace all of it with blow cellulose. My thought is my roof line can only give me 5″ of insulation, and this would be inadequate for the region.
Finally, what are your thoughts on the DIY closed cell foam kits? Obviously doing a whole house would be impractical, but if I do this my self using rigid foam blocks and/or foil-faced polyisocyanurate at the roof rafters, would the DIY closed cell foam kits be sufficient quality to bridge gaps and irregular areas?
Thanks.
Hi Chris, thank for the kudos.
Nola is certainly a challenging climate, with extreme heat and humidity. You face different challenges than us northerners. Up here, the big concern is allowing interior humidity come in contact with cold surfaces during the winter. Down there, you’ve got extreme summer humidity that can condense on cooled interior walls.
Sounds like a heck of a house. I wouldn’t want the HVAC in an attic down there, even one so well vented. As you asked, doing a sealed attic/insulated roof does indeed make sense in that situation. In your climate, I’d be less concerned about the open-cell vs. closed cell question. That’s more of an issue in cold climates because of condensation risk. However, the closed cell will give you the greatly increased structural integrity, as you noted, since it is essentially gluing the roof sheathing to the 2×6’s supporting them, and you get double the R-value which would be pretty important.
I wouldn’t want to go the route of insulating under the roof then again on the attic floor. This can create a “dead air space” that can be problematic. I’d scratch that idea.
Polyiso isn’t a bad approach. With its r-7 per inch, you’ll get about R-40 if you fill the space between the beams. You could then seal everything with the DIY foam kit. I’ve used a bunch of these and, as long as the canisters are warm (80-100F is great), they spray really well. It takes a little getting used to, but if you’re just doing a skim coat to seal things, you can make it go a pretty long way.
Just to make sure I didn’t miss anything in this short answer, I would strongly suggest you buy Building Science corp’s “Builder’s Guide to Hot and Humid Climates” – these go through all the considerations of doing this type of thing. You sound like a smart guy so you’d probably get a lot out of it. Or, just go to buildingscience.com and look at their papers on insulating attics in your climate.
Good luck!
Thanks Ted! The Building Science site is a great resource. I have read through a few articles. It seems though a lot of the articles geared to Hot and Humid Climates are targeted at new construction; a lot of the retrofit articles appear to be geared in the colder climates. You certainly understand the challenges one has in a retrofit, especially a finished 1-1/2 story, then compounded with 2×6 raters. Could you help me clarify some issues?
First, there is a lot of conflicting information regarding application of foam to the underside of the roof sheathing. Are you under the impression that this is not a problem in the south hot-humid region? In regards to closed vs. open, there are many contractors advising open cell under the roof sheathing in case of roof leaks so that the underside of the deck can breathe. As I stated before, many of these open cell contractors then explain the importance of air sealing the rest of the house attic space, of course at great expense. At the same time, the closed cell industry is stating closed cell prevents the underside of the decking getting damp even if the roof leaks, thus it’s better. The most recent article I read indicates the issue is moot as even with closed cell, the wood can still breathe enough that it would not rot unless the moisture source was constant and not repaired. So much conflicting information. I would appreciate if you know of any non-biased sources that can clear this up.
Secondly, if the closed cell really is right choice, would using rigid foam to fill the rafters cavities with spray foam in the gaps and irregular places be more cost effective then a whole spray application? I like the guidance in your forth paragraph and assuming this would be a more feasible and cost effective DIY approach. If I did this, would foil faced poly board still provide benefit, foil down of course?
Lastly, in the 3-ft of cathedral ceiling I have, should I remove the fiberglass batts and replace with rigid/closed cell? This would be difficult to do without removing the drywall, but looks like it can be done with persistence from the crawl space.
Regarding the dead space. If I can get better than R-30 in the roof rafters, then yes, I would scratch the idea. My initial thought was if I used open cell as advised by insulations installers, I would not hit R-30 and would still need to fix the insulation in the attic. I dont agree this would be dead space as my duct work is in the crawl space and very leaky. Obviously, I would have to allow for some controlled HVAC in the attic when I correct that issue as well, which I plan to. But also, I was under the impression the cellulose would not provide an air seal, so the attic would still breathe from the house, just no longer through the roof.
Thanks for your help. And again, great website!
Argh, I just wrote a really long reply and lost it. I hate when that happens!
– Foaming to the roof deck is controversial. I prefer designing a solution that is less controversial but based in sound theory. My preference is to install 1″ spacers under the deck (nailed to the rafters). Then, install board foam right up to the spacer. This provides an air gap under the roof deck so it can still be ventilated from soffit to ridge but isolate from the rest of the attic. Best of both worlds. And, you don’t have to worry about the roof deck being glued together if you have to replace any in the future. This also provides a durable surface (the back of the foam) for water to drain down if there’s ever a leak.
– Closed cell is about double the cost of poly-iso board foam, so if you’re going to DIY and pay yourself $0, you can save a lot going that route. If it were my roof, I’d install one layer of foil face, with the foil facing up, so that you’d get the radiant barrier effect directly under the roof (into the air gap formed by the spacers). Then, I’d use less expensive poly-iso board foam to fill in the rest of the rafter space. My preference would be to spray the underside of everything with foam so as to provide a good air seal to the entire assembly and reduce thermal bridging through the rafters. Doing this would give you about a full R40-R45 even with that air gap (R7 * 4.5″ deep plus R10-R15 of spray foam under that)
– The catherdralized sections are always a pain. Personally, I would sacrifice the drywall and do it from the inside. Working in the attic, trying to do a good job through that little gap is a real pain! You’ll never do it just right and get things to seal well.
– Breathing attic – you’re probably right. The main places I’ve seen people get in trouble is when they spray foam air seal attic spaces and create dead spaces with zero ventilation possibilities. That can be very problematic.
How does the fujitsu rls work in a damp snowy condition? right now there is so much snow (mostly slide off the roof) the only windows to see out of are in the gable ends of the house (which is where the doors are, since this happens every winter), but other than the obvious question of siting it at a gable end (so it isn’t buried in snow), is the fact of living in a cold temperate rain forest climate likely to make it unuseful due to constant defrosting?
That’s a good question. If you do have a dealer in the area, I’d ask for references so that you can talk to other people who have to deal with the same conditions.
The defrost cycles are definitely an annoying and limiting factor when you’re in the humid and 25-35F temperature range.
At the least, I would want to make an elevated platform to support the units out of the snow or provide a nice overhang that minimizes the snow buildup around the units.
I am building a new house near St. Louis, MO, midwest hot humid summers, moderate winters. I have a great room with a cathedral ceiling insulated with fiberglass bats (due to the steepness of the roof). I plan to install toungue and groove pine on the ceiling, and not drywall. My question is, do I need to install an air barrier? My concern is that T&G wood will be too pourous and will allow too much heated air to escape, but I also don’t want to trap moisture somewhere where it shouldn’t be.
Ken, I urge you to read my post on this very topic: https://tedsenergytips.com/2011/03/13/cathedral-ceilings/
I’ve seen a number of homes constructed exactly in the way you describe and they’ve all been disasters. You hit the nail on the hid when you wrote “My concern is that T&G wood will be too pourous and will allow too much heated air to escape, but I also don’t want to trap moisture somewhere where it shouldn’t be.”
The short answer is – if you really want a T&G ceiling, spend the extra money and use closed cell spray foam. But really, please read the above article. This is something you really want to do right.
Hi Ted,
I installed a dual Fujitsu heat pump system last year and it has saved us $1000-1300 vs oil heat for the rear portion of our house vs. last year. I am wondering about the similar technology for hot water heating and for augmenting/replacing the oil fired boiler that heats the remainder of the house – as well as the electric hot water heater. For the latter, there is something called the airtap that looks interesting. For the former, I wonder if it makes sense to try and also use this technology to entirely or mostly get rid of our reliance on oil for heating the primary system – old cast iron radiators. The hot water heater in in our basement in a heated area under the master BR, and the boiler is also in the basement but in the rear of the house, under a living room/family room.
Jeff,
There is at least one solution – the Daikin Altherma air-to-water heat pump: http://www.spacealtherma.com/
I haven’t personally had any experience with it but there’s no reason why it shouldn’t work.
However, there is a reason why it won’t work as well as your Fujitsu heat pump – operating temperatures.
Here’s the deal. With an air heat pump like our Fujitsu, you’re raising air temperature from 70F up to maybe 100F. When you replace a boiler, you need to produce very hot water, typically 160F-180F. This is much harder for heat pumps to do. Normally, you limit hot water generation to about 120F, maybe 130F in order to maintain reasonable efficiency. Because of this, heat pump technology isn’t effective for heating water for use in radiators. This includes geothermal systems. You have to look at a more significant heating system change in order to make this all work.
As for general hot water, typically you’re running a water heater in that 120F-130F range, so heat pumps can do the trick. I have an AirTap water heater (though I haven’t used it in a while because the thermostat broke). When it was working, it was great – very efficient, especially during the summer when it could cool and dehumidify my basement. But you have to keep in mind that putting a heat pump inside the house has its downsides – in order to make hot water, it cools the air around it. So during the winter, this is essentially an air conditioner in your house running so you have to heat more to counter-effect the AirTap. So I typically switched to a different heater during the winter.
Nothing’s quite as simple as it seems unfortunately!
Hello Ted….
I just found your blog…..
For the first time in my research on the Fujitsu 12RLS I have found an answer to
a question I have had (while reading Jack Leonard’s post on the 18th) regarding
output temperature of the unit at sub-freezing outdoor temperatures.
Do you have any additional stats to confirm his information?
Thanks,
Ron
Ron,
Yep, I’ve actually got temperature sensors (input and output air) on two of my units as well as current sensors so I can see how much they’re drawing, so I’ve been able to monitor their operation continuously since installation.
The air they supply to the room is almost always between 95F-105F – quite warm even in cold outdoor temperatures. The only time the put out colder air is when they run defrost cycles, but then they turn the fan way down or off so it’s not blowing cold air around the room.
Part of the trick is that they vary the fan speed. So the temperature may be high but the fan speed is lower so the total heat delivered to the room is less as the outdoor temperatures drop. But pretty much everything I’ve seen confirms the manufacturer’s specs and it performs admirably at low temperatures.
There is one independent study that measured performance at a variety of temperatures that validates the specs
http://www.nrel.gov/docs/fy11osti/52175.pdf
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Ted –
I saw your video on the Fujitsu 12 RLS heat pump. One point you did not discuss is the level of noise produced by the appliance inside the house. How does it compare to, for instance, to the sound of a conventional gas furnace blower that comes through the floor duct, or maybe a standard window fan?
Thanks
Mike
Good point, thanks for asking.
If you let it run on “auto” and don’t push it to hard most of the time, that’s equivalent to low or medium fan speed which is very unobtrusive – a gentle fan sound that you tune out. Probably about equivalent to my central heating system blower and much quieter than a typical window fan. However when it is on full-blast, it’s pretty loud. Not like a window air conditioner, but loud enough that some would complain about the noise levels.
Morning Ted, I just had to let you know what great equipment this Fujitsu 12RLS is once again. Listen to this. Last night temps here were in the -1 to -3 degrees C with heavy rain and freezing rain. Overnight the temp plunged to -20 degrees C and everything froze solid. It took me an hour to get the ice off my car and I thought I had broken the wipers in the process but I guess the mechanism was just iced up and the running engine helped thaw them out. This morning temps are -15 but the killer is that the wind is 40 kilometers per hour gusting to 60. This gives a wind chill well below -30C. Now Ted these are rough conditions by any measure, the Fujitsu is unfazed by it all. Its down there in my kitchen right with output temps at 98 to 100 degrees F. I’m confident those numbers are good as I’m now using a laser pistol type thermometer which I can point right into the outlet vent. The 12RLS is maintaining my kitchen and dining area at a nice warm 72F which is what the remote is set for.
The next few days promise to be quite a bit warmer getting up to the seasonal daily average of -6C.
The Fujitsu could care less.
Regards
Jack
Ted,
I am finally getting around to installing a roof-vented bathroom fan as the first step in decreasing winter moisture in my attic. Once that’s done, I’m going to get additional insulation blown into the attic (currently R19 bats of ~40 year vintage) as a precursor to replacing our 40 year old boiler/hydronic system with geothermal some time in the next 2 years. Our attic currently has flooring down the middle (was used for storage- I don’t store things in attics). Is it better to have loose fill piled on top of the plywood, remove the plywood, or have the area under the wood dense-packed?
Ok, this is an ideal time to check for other air leaks between your living space and attic. Do NOT blow in insulation before doing this or you’ll regret it. I nearly killed my insulation guy who thought he was doing me a favor when he blew about 16″ of cellulose on top my already insulated attic, making it very difficult for me to work up there! Trust me on this.
If you want to “do it right”, you’ll locate all the wire penetrations and electrical boxes and other hidden holes and you’ll seal them while it’s easy. Then you’ll re-insulate afterwards. Also, if you ever plan on running new wires, light fixtures, etc., do it before blowing insulation in there. It’s a real bugger to work in an attic full of loose fill.
As for the flooring, you really could go any route you mentioned. In my own attic, I kept a narrow walkway between my attic access, down the center of the attic and to my air handler. I stuck batts under the 18″ or so of walkway and then have the blown in stuff covering much of it. This way, when I do need to run wires or do work up there, I just sweep the loose fill out of the way and have a safe access across the attic rather than trying to balance on the joists.
Thanks again for your thoughtful reply. I should have specified that we’re insulating following foam plugging of air leaks and placement of vent chutes (we had 36 soffit vents added last summer and covered the gable vents so that the ridge vent might work right) – I checked with our Angie’s List- multiply-approved contractor to ensure this would be done. While we may be adding a forced air system at some point with the geothermal, I’m interested in getting the insulation advantage now and I’m sure HVAC guys are used to crawling around in attics full of the junk, right? One last thing: the access to the attic is up a stair/shelf in the closet with a ~4X8 sheet on hinges as the door/hatch. Any good suggestions on how to weather-strip/insulate that to make it somewhat more air tight?
Excellent, sounds like you’re doing your homework! It’s great to have these discussions publicly so others can see the thought processes that go into “simple” things like insulating your attic. I’ve had a number of people call me and say “my contractor thought I should call you to get your guidance, but I don’t know why. I just need to insulate my attic.”
The HVAC guys should be used to it, but they’ll certainly be cursing you under their breath 🙂 But this is a good reason to leave the walkway/floor in the attic. Last thing you need is a foot going through the ceiling.
Question – it sounds like you don’t have forced air now and you’d be adding ductwork etc. to the attic in the future. You might consider having registers “stubbed in” before doing the added insulation. It does make it much more of a pain (and more expensive) to install all the ducts after a blown in insulation job. You’re also more likely to have them poorly air-seal the registers because of all the insulation.
I’m sure you’ve thought of this, but I’ll mention it for our other readers – if at all possible, you’re best off installing air handlers and ductwork in the basement rather than the attic. Doing work on attic-mounted systems is a hassle. “Hassle” translates to greater cost and increased opportunities for poor workmanship. I know this from personal experience. Virtually every attic mounted duct/air handling system I’ve seen is much more poorly installed than basement mounted systems because it’s out of sight. If you can’t see it, you’re not going to inspect it and the contractors know this, so they’ll take shortcuts.
In addition, attic mounted systems are less efficient than those mounted in the “conditioned space” of the house. Not only are the systems subjected to temperature extremes, but any leaks (which all systems have) will be outside the house. Finally, the leaks will often suck in the nasty attic air, leading to a dustier/dirtier home.
On the attic “hatch” – those systems are often a hassle. If the plywood and opening are uniform, then just some good weatherstrip installed so that it gets compressed when the hatch closes can work well. Plus, a few inches of board-foam attached/glued to the attic side of the hatch. Usually though, these hatches are pretty clunky and it’s quite tough to air-seal them effectively. If yours is like that, it’s worth re-mounting it so that you have a nice flat surface and the hatch closes with a uniform gap of about 3/16″. Then a compressible “D-profile” weatherstrip works great.
Ted,
First off, you have a great page not just in information, but in overall design. I have a question for you and haven’t been able to find a good answer yet. I live in a Upstate New York home built in the 30’s. The previous owner decided to add an attic bedroom, but they didn’t insulate correctly.
The attic has your basic knee walls, improperly insulated with exposed pink fiberglass on the unfinished side. That is going to be easy to fix. I cut away some of the floor on the finished side to see what was under it. They left kraft faced R-22 spanning the joists between floors (2x8s). It was clean so I’m guessing air movement is minimal. Would it be beneficial for me to remove some of the floor and properly block below the knee walls?
My goal is to make the room more comfortable and energy efficient. I would like to get a return on my investment, but may not live here much longer than another 5 years. Does the work sound worth while?
Thanks Chris, I appreciate the feedback!
Those attic rooms – ugh, everybody seems to do them wrong.
If you can get behind the kneewall to see the insulation, work from that side. Usually the cavities are open and easily accessible for air sealing. The quickest/easiest way is the “insulation pillow” – fill a kitchen sized garbage back with insulation and then pack that in the gap under the kneewall to form an air-tight plug.
On the back of the wall, I know some contractors who will use 2″ rigid board foam affixed to the knee wall studs. That insulates the studs to minimize the thermal bridging and holds in the fiberglass that’s in there so you double the benefit giving a knee wall R-value of about R-20. An alternative is to insulate below the rafters and not on the back of the kneewall. Depending on access, this may or may not work for you. See the link at the end of my reply for a diagram.
Doing these two should be a cost-effective weekend job if it’s a modest sized space.
If you can, you should also take a look up the sloped ceiling (from the attic side) and see what’s going on in there. Most homes of this vintage will either have this space packed with insulation or have nothing at all. If it already has insulation, and the roof shows no sign of moisture damage, don’t touch it. I don’t like messing with things that have been working for decades. If it doesn’t have insulation, this can be a tough retrofit. Without insulation, those sloped portions will bake in the summer and freeze in the winter. There’s some serious thought that has to go into that retrofit because done incorrectly, you can end up with a rotten roof.
I’d suggest taking a look at the following link for some ideas:
Thanks for the input. There is enough space behind the wall for me to crawl and repair. I actually did what you suggested with the rigid foam over the studs (in a small test area) a few months ago. There is a lot of conflicting information on the internet, and some of it indicated that I was just going to create a moisture problem between the XPS board and the faced insulation that is currently in the knee wall. So I stopped and decided to research more.
I was considering a 600 bd/ft spray foam kit. I was thinking about cutting out the fiberglass on the knee wall and using a combination rigid foam and spray. Does this make more sense? I liked this hybrid route because of the cost savings. If this does make sense, can I do a 2″ XPS board in the wall and then cover the rest of the space (and the 2x4s) with an inch of spray foam to air seal?
Back to the attic floor. The crawlspace has decking over the joist and I think it may be too small a space to comfortably work and cut away the decking. Would it be worth it to do that work or should I leave it and spray in cellulose on the deck floor after I am done addressing the knee wall? If a picture is worth 1,000 words; what would a YouTube video be? The video probably helps explain it a little better.
Hey, awesome! A video really does tell the story.
That’s a familiar looking knee wall/attic space. There’s probably millions out there just like that.
Regarding moisture – you do want to avoid the “double vapor barrier” trap, so faced insulation + board foam can be a problem. It’s not likely to be one, but for safety, it is best to use unfaced insulation or remove the facing from the fiberglass. Of course, then people will complain because the vapor retarder is supposed to be on the “warm side”, meaning facing the inside of the house. If you strip the facing and then use XPS, you’re effectively putting the vapor retarder on the cold side.
On your spray foam question – that approach would work quite well. If you’ve got a table saw, you can rip lots of XPS into strips to go between the studs then just spray over it to lock in the goodness. I’ve used quite a few of those foam kits and they’re a bit finicky. At the end of the day, I usually wish that I’d just called in a professional foam contractor to do the job! Small jobs like band joists are great, but this is a pretty extensive area. I’d say it’s on the border between DIY and call in the pros.
Personally, I prefer the approach of insulation under the roof for these types of attic spaces. While your setup is the most common, there are enough leak points that it can be a real pain to properly insulate everything. Insulating under the roof and bringing the attic into the conditioned space of the house can be much easier and more effective. I’ll try to write up a full article on this soon.
In a nutshell, here’s what I’d personally do:
1) ensure proper soffit venting and clear air pathway up to the top attic and its venting (you’ve got chutes there now, so I’m assuming this is a-ok but you should double check)
2) Install 1 1/2″ to 2″ spacer blocks under the roof sheathing to serve as an air gap from the soffit to the existing chutes
3) Install a couple layers of 2″ XPS in between the rafters, leaving an air gap from the soffit vent up above the insulation
4) Spray foam under the rafters and XPS to seal everything up air-tight. Or, just add another layer of XPS. Spray foam seals things up better, so I prefer that method.
See this link for some diagrams:
http://oikos.com/esb/51/sideattics.html
Hope that helps.
Thanks for the response. That was a helpful link. I like the idea of doing the entire roof deck. I’m not sure if it will be within budget. Using the roof deck/foam/spray method, I will have a difficult time meeting the R-49 requirement for my zone. I would be closer to R-25 with 4 inches or rigid foam and some spray. I’m guessing that combination may out preform R-49 fiberglass with air leaks.
I will probably cut out the sheetrock on the center of the roof, but I won’t be able to spray over the rigid foam between the sloped rafters (because the room is finished). Not being able to seal that portion of the roof will cause some air leakage. Is this still an acceptable method without being able to seal it up?
That little section from the top of the knee wall to the flat section of the top attic is always a problematic section because of existing finished ceilings.
The “safe” approach is to to provide continuous ventilation under the roof deck all the way up to the peak from the soffits. If you’re using rigid board foam with furring strips mounted to the rafters as spacers, you can re-pack insulation in those sloped areas and spray right from the top of the knee wall to the bottom side of the foam. That will also help the non-foam insulation in the sloped areas perform better because air won’t be moving through it.
Instead of XPS you could use polyiso board foam. The R-value can’t be beat at around R-7 per inch (there’s some controversy around the exact R-value). It’s more expensive than the XPS but if you want to squeeze out every bit of R-value, you can’t beat it.
One other thing to look at is the “whole-wall” R-value (actually, whole roof in this case). If you fill the cavity minus the air space with board foam then spray foam over that and cover the rafters with an inch or two of foam, you’re vastly improving the R-value of the rafters, which would otherwise drag down the total R-value in the normal situation because the rafters lead to thermal bridging. That’s what’s going on in the sloped section that you can’t do anything about. In the rest, as you note, you’re not going to hit R-49, but also as you note, I’d take R-30 of polyiso sealed with spray foam any day over R-49 of loose fill or batts installed normally. There’s some good charts here: http://www.monolithic.com/stories/r-value-fairy-tale-the-myth-of-insulation-values/photos
In particular, check out the R-value vs. temperature graph. Fiberglass loses substantial R-value with temperature – not a great characteristic for insulation!
The level of insulation in justice’s home is truly impressive! I can’t get any more in my walls – would have to reside the whole house and put foam panels on the outside. If my house could be jealous, it would be!
Ted,
You’re welcome! It is a personal mission of mine to encourage and teach about saving energy. Thanks for correcting the link.
Ted, here is something I wrote up about all the work I had done in 2006. It has a link to the Cool Vent panels.
After comparing the energy audit results and recommendations of three different contractors in 2006, I chose one of the companies to complete the majority of work that needed to be done to make my home more energy efficient. (Other contractors completed smaller jobs.) The main contractor initiated the paperwork necessary for me to receive not only a $6,000 Energy Star grant, but also a 4% low interest loan through NYSERDA. Here is a list of the work done:
1. Replaced original 1950’s era gas furnace with new high efficiency model
2. Replaced a nearly 20-year-old refrigerator with an Energy Star model
3. Replaced a 1970’s era (avocado anyone?) washer with Energy Star model
4. Replaced 4 ten+ year old low-quality vinyl windows with Energy Star windows (remainder of windows already replaced with triple-pane vinyl windows)
5. Replaced 6 single pane basement windows with glass block windows
6. Added AirKrete ® http://www.airkrete.com/ insulation in all exterior walls
7. Added foam insulation to all rim joists, and under house wing over garage
8. Replaced rear and side exterior doors (front door already replaced)
9. Finished installation of Hunter Cool-Vent TM panels on roof over vaulted ceilings http://www.hpanels.com/pages/cool-vent_articles.html
I now have a year’s worth of data on the resulting energy savings, from my local utility’s website showing my home’s energy use over the past two years. My gas usage in therms decreased by 25%. My electricity use in kWh decreased by 44%. Not too shabby, and I still have things to tweak!
……………………………………………………………………………….
My electric use over the past year (12/07-11/08) has been 3,383 KWH, which is 44% less than before all the work was done. 3,383 KWH times .095 rate for renewable/green electricity = $321.38 + RG&E delivery charges (varies). My gas use of the past year was 522 therms. That is 25% less than it was before the improvements. 522 therms times $1.305 per therm = $681.21 + RG&E delivery charges (varies). All totaled, my utility bills over the last year were about $1480.00. [This would be a lot easier to figure out without RG&E’s separate delivery charges!]
Margie, thanks so much for sharing. Kudos on a successful energy-efficiency renovation!Your savings are impressive. It’s really meaningful to share ‘real-life’ information like this. I think a lot of people are skeptical and think that all these things are theoretical. Keep up the great work and keep spreading your successes.
By the way, it looks like they changed the link to the panels. Here’s a link to the page of products.
Ted: we bought a home that has 3″ rigid foam (owens pink) that was cut between old timbers and foamed tight to the exterior wall. The builders then built and insulated a 2×4 wall inside the old wall to provide a flat wall and add insulation value. This wall was insulated using r-15 Roxsul brand insulation, and a 6 mil vapor barrier before sheetrocking. When we cut into the wall to add an outlet for TV, there was moisture on the inside of the poly where it contacts the Roxsul- not much, and only on the south side. I asked the builder who did the work, and he said he didnt want the vb but code said it had to be there. They had to keep the historic exterior, so they couldn’t add rigid board to the outside. The building inspector indicated that he required the vapor barrier per code against the builders wishes…. now what do we do? What is right? Dubuque IA
When you say inside, do you mean facing the sheetrock or right against the roxul?
That sounds like a pretty tough situation. The rigid foam is slightly vapor permeable but clearly not compared to the vapor barrier! Most building science folks push for removing of those building codes that force the blind use of vapor barriers exactly for these reasons.
The strange thing is that the moisture is condensing near the inner wall. That’s a big concern because that’s a red flag for a LOT of moisture being trapped in the walls.
I’m assuming this was during the winter?
On the south side is also suspicious. Sometimes this happens when the sun “pushes” the moisture through the wall, especially with brick exteriors which can act like sponges for moisture. What is the exterior of this wall like?
The more information you can provide, the better.
So far, we have only found it on the roxsul side of the plastic, only on south side. The exterior is only limestone and concrete foundation, clapboard siding on bottom of framed walls, gingerbread above windows/gables. Exterior also has a double layer of aspalt felt, thicker than current 30lb. We found this putting in exterior outlets. Did a larger inspection hole inside, roxsul and pink are dry- less than 7-12% once past the outer boundry using moisture meter- so the moisture is definately at the poly and roxsul. Did 3/8″ drill holes in wall along the top of the stud cavities, where they would be covered by new crown, and some have moisture marks 2 days later. Builder did this wall when high humidity in summer, and no AC. AC was used after drywall was sanded before painting and floors- his thought is moisture is trapped in cavity from this summer period, and has migrated to the interior face. NEW inspector agrees with builder- no vapor barrier, only housewrap on interior if desired. Rafters and plate area are foamed with close cell up top; the house has 6″ polyiso board on top of old roof deck, and iso board cut between full 3×6 rafters. We did some test readings there and up on roof via ridge and other points- all were less than 10% moisture. So at least it’s limited to south wall!
My only thought now to solve is to drill holes at base and behind crown area to let wall breathe, otherwise we have a project in taking down drywall and removing the interior vapor barrier. Or put a whole lot of holes in wall with drill, then mud and repaint! Hope you might have some other points to ponder on this…
You question/situation is so interesting, I’m going to turn it into a full post. Stay tuned for the full report!
Ok – another article done!
Let’s continue the dialog in the comments of the new article.
I wanted to follow up with you to see if you saw my article addressing your moisture issues. I’d be very interested to learn what you discover as you do work on your walls. This could be a great learning experience for others and help them avoid similar issues in their own homes.
Here’s the end result: we pulled the drywall off, and the poly. Out came the roxsul just to chek for any other issues, such as leaks, etc. Nothing was found, and the roof is brand new, no water issues were seen on the foam or foam side of the wall, or near the roof plate. The moisture meter reading was less than 7% overall on the old timbers where they were probed. One interesting thing to note from the builder- the home was pressure washed by the lead abatement crew to remove any dust and residue from lead items (Dubuque area commonly used lead mine leftovers for mixing plaster, cement, etc.). Again, this was in the summer, and the builder began right after the crew left. We only found the moisture on poly right at the roxsul; nothing in the roxsul or past towards the foam. In fact, even with no wall/insulation/vapor barrier, the wall is warm to touch from the sun hitting the exterior (historic gunmetal grey paint- explains the heat that is absorbed)
We are letting the wall breathe out now, and next week we are reinstalling the roxsul and drywall, and NO vapor barrier. All the moisture seemed to be on the poly, where it couldn’t escape as it was sealed tight. As a note, no other walls in the old part of the house had this same issue. However,the other walls are getting holes drilled in the drywall and through the poly, just make sure they can breathe as well.
As the previous inspector order the wrong things to be done despite the objections of the builder, we are asking for a refund of a portion of the permit fee, which is about the most we can do in this case. Like you stated, drywall and paint are inexpensive! (plus, we can add the outlets we wanted, which is what led us to discover the issue in the first place! Bonus!) As a note the energy efficiency of the home- our furnace rarely runs- the wood stove heats the home, and the house is so well insulated that even with no fire going, it took over 36 hours for the interior temp to drop from 73 to 65 with outside temps of 20 to 40f. Someone forgot to turn the furnace on when we left for Christmas!
Thanks for the report. Very interesting and still perplexing! Please share if you learn anything else in the future.
Good luck!
Hello Ted, another report from the “frozen” north. If you think you have enough info on my experience with the 12RLS let me know, I don’t want to get boring. I will try to give temps in both celcius and farenheit so as not to confuse anyone reading this. Canada changed to C back in the mid eighties and I have mostly mentally converted. The remote for the 12RLS is just in F as near as I can find out.
The morning of the 29th Dec here was quite cold -23.5C (10 below 0 F) but was clear with a calm wind. At 7:30 AM I ck’d the output of the 12RLS which was at 35C ( about 97F).
I usually keep the 12RLS set at 74F which seems to keep the area I want to heat at about 24C (about 74F) which seems to be comfortable most of the time.
At about 8:30 AM with the outside temp still at about -23C I upped the temp control on the 12RLS remote to 76F, within a few minutes the unit was putting air out at 39C (about 102F?) with a greatly increased fan speed.
The temp that day stayed around -18 to -19C (3 or 4 below 0F) and the output from the air handler maintained at about 35C with the remote set back to 74F.
My observation so far is that the heat pump does better on clear, dry days rather than on a day like today which is cloudy with snow flurries and high humidity.
Today while the temp is only -12 or 13C the heat output is still at about 35C.
Well Ted I hope you and your readers fine this info useful?
Jack
Jack, it’s always good to hear from you. I’m a data junkie so I never get tired of this. Plus, there’s nothing more valuable than actual field experience to help others who might be considering a similar setup.
The more you say about your experiences the more impressed I get. I’m alway very conservative recommending heat pump technology in cold climates like yours, but it really seems like the Fujitsu is working well.
Your observation about the type of weather matches up well with the theory and my own experiences. In more humid weather, the heat pump coils will freeze up more, requiring additional defrost cycles and lower overall heating effectiveness. With dry air, the system can crank away without the performance degradation.
Cheers,
-Ted
Thanks for the info Jack, I am really surprised to see the 12RLS performing that good in frigid Canadian conditions. It gives me confidence that a mini split heat pump would perform well here where the temperature rarely gets below 0F(-18C). I am in the process of looking for someone that will sell me a Fujitsu 12RLS. I would like to avoid some of the high installation costs and equipment markups by doing part of the instillation myself and letting the contractor make the line set connections, do the pressure test, and vacuum the system.
Due to Fujitsu’s strict “dealer sales only” policy it might not be possible for me to install any part of the system or even find an HVAC contractor the sells Fujitsu products in my area. Hopefully other manufacturers’ heat pumps will perform as well as the Fujitsu 12RLS, although the 12RLS has the best SEER (25) and best HSPF (12) of any mini-split I have looked into.
Check into the Daikin units as well. Check out this link. Maybe you could find someone to install one of those.
There are some sources on the web where you can buy the 12RLS for under $2000 and if you’ve got a cooperative HVAC contractor, you could do much of the work yourself. But as you noted, you’d be unlikely to get a warranty.
Mitsubishi has an extensive line of mini-splits though the performance specs aren’t as impressive. But they’re considered the workhorses in the industry. For heating, be sure to focus on the HSPF rating rather than the SEER. Though they typically go together, the HSPF’s may not vary as much as might be indicated by the SEER’s.
There are also some units that have a “turbo” mode for when it gets cold. You lose some efficiency, but that’s less important than heating capacity when you’re just trying to stay warm.
I can’t find a Fujitsu dealer in Northern Ohio. Did you have a local Fujitsu dealer or did you have to get them some other way? Thanks.
I had a local HVAC contractor supply them.
There should be someone in your area qualified to install them.
Try calling Fujitsu and asking for an installer near you.
Hello Ted, well since I last wrote to you just after having the 12RLS installed (Dec 14) we have had a wide range to temps here. All the way from -15C to +5C, sorry I’m going to give temps in celius that is what I’m used to and all my themomters are in C and thats how I’m recording temps. Anywat during this great variation in temps I have seen output temps in the 35C to 41C depending on the outside temps I guess? For instance on 18 Dec the outside air was -15C and the units output was 37C, on 21 Dec with an outside temp of -3C the output was 41C.
I keep the remote @ 74F and set on AUTO.
What I am most pleased about is that it is keeping the rooms I wanted to heat with the 12RLS at about 74F pretty constantly. Today for instance its really brutal ot there the temp is 12C and heading lower but the wind chill is already -22C and that is cold for 3 in the afternoon.
thats it for now
best regards and happy new year
Jack
Hi Jack, that is an excellent New Year’s message. I’m really happy to hear that these are working out for you so well. I’ll bet Fujitsu would be as well.
You’ve got it right – the maximum output temperature of the system will be directly related to the temperature. I’ll tell you, 37C output from a heat pump when the outdoor temperature was -15C is spectacular. From what I’ve seen in conventional heat pumps, you’re usually lucky to get 30C at those outdoor temperatures.
Thanks so much for the report. I’m sure others will be very interested in this.
-Ted
Hello Ted, you have answered a couple of my questions about the 12RLS and this week I had one installed. The first couple of days the temp was about 0 F but last nite it went down to about 10 F and has not warmed up much today and the Fujitsu is performaning well, I have an older home on three levels with variable degrees of insulation, all new windows. The unit is on the lowest level of three and is just outside my kitchen window and the indoor air handler is just a few feet away (6′) over the kitchen sink. Its keeping the house nice and warm but I am wondering what can I expect as the weather gets colder? I just noticed a little while ago that it went into defrost cycle for less than 10 min. and when it restarted the fan came on a what seemed a higher output than normal when set at”medium” I chkd the output air at the unit and it was about 94F with the remote set at 74F. Is that normal in you experience? I was disappointed with the manual that came with the unit. very little about how to operate it for peak performance, and nothing on what to expect with varing climate conditions.
Thanks for your help Ted
Jack Leonard
Ontario, Canada
Hey Jack,
Thanks so much for writing. Glad to hear that the Fujitsu is working well under such harsh conditions! I haven’t pushed my units that hard, so it’s great to hear from you.
The defrost cycles get “funky” – expect some strange sounds and fan operation during that time. I’ve found that my unit suddenly goes to defrost, the fan cuts out and then it works overtime when the cycle is done. So the behavior of your unit sounds “normal” from my experience.
The output air depends on a lot of factors, but typically, I get 100-110 degree air out during moderate temperatures outside. When it gets colder, the system has to work harder, so 94F sounds in the right ballpark.
My expectations these days for manuals are pretty low. I would have liked to see more also. Pretty much, I just set the units to “auto” and put the temperature around where I want it to be, and let it do it’s thing. You’ll definitely notice diminished output as it gets colder. With heat pumps, 50% decrease in overall heat output when the air drops to 10F is not unusual. These mini-splits with inverter drive compressors do better because they can push the compressor hard at cold temperatures but you’re still fighting physics. If you get appreciable hot air out when it’s under 10F, consider yourself lucky 🙂
I hope you’ll report back and share your experiences as the temperatures drop.
-Ted
what outside temperature does not work on a 12,000 btu a/c heat pump. we live in montreal, qc.
tnx j.s.
Hi Jerry,
You’ll have to check with the manufacturer’s spec sheet on your unit. Every unit has an ‘output curve’ that defines how much heat it can deliver based on outside conditions. For example, there are some modern units that are designed for cold temperatures and can put out a good amount of heat even at 0F. On the other hand, some normal system drop down to about 50% output when you get to freezing temperatures.
Typically, when you’re about five to ten degrees below freezing to about five degrees above freezing, heat pumps struggle because of the need for defrost cycles. If you look at the outdoor unit at these temperatures, you’ll see a lot of ice forming on the coils. The unit has to run in reverse periodically to melt the ice. When it does, it actually puts cold air into the house and heats outside.
However, the overall efficiency of a heat pump, even at these conditions, will be higher than using a normal electric space heater. So even when it’s somewhat cold out, you’re best off using the heat pump and supplementing it with other heat as needed.
Check with the manufacturer to see what range of temperatures they recommend.
Hi Ted
I recently had a pair of Daikin Quaternity mini split heat pumps installed. A 9k for the master bedroom and a 15k for open area entry/living/dinning/kitchen.
Extremely happy with my choice but wondering if a behaviour issue is common to all mini splits. I read your review on your Fujitsu RLS. Do yours or any of your followers have this same issue:
Both heating and cooling will move approx 5 degrees F passed the set point. e.g. I set my units to 65F to maintain a room temp of 70F as measured on my aux heating tstat and another I have for a propane f/p. At the same time the display on the Daikin remotes indicates that the sensor on the wall mounted (8 ft ceiling) indicates 72F. Both units behave the same.
I can understand the extra 2 degrees on the sensor, based on heighth but is the 5 degrees passed set point not a tad excessive?
Those look like excellent units. Actually, they look almost identical to the Fujitsu, so I wonder if they’re the same unit with different covers?
As for your set point issues – I do adjust mine based more on the stat near where I sit rather than the number on the unit. But in part, that’s because the units are mounted in somewhat strange locations, so that will confuse the issue.
For example, I had to mount my living room unit near the floor instead of high on the wall. So the unit is measuring the floor temperature rather than the ceiling temperature. With typical stratification of air, you might have a five degree temperature difference between these locations. Is seems like you’ve already thought of this. Five degrees does seem excessive.
In my experience, the temperatures are pretty accurate overall. In my bedroom, where the unit is mounted on the wall, the temperature setting and the wall thermostat match up within a degree or two.
So the quick answer is, 5 degrees seems excessive, assuming that you’re getting good air mixing in the room. Is this a problem? Not really, it’s just an arbitrary number. As long as the units keep the temperature consistent, I wouldn’t worry about what it thinks the temperature is.
thanks Ted.
you’re right about the similarities between RLS and Quaternity. RLS was my 2nd choice, I went with Daikin based on the Dehumidification capabilities. Being able to lower humidity without lowering temperature seemed a nice option for our region in Nova Scotia.
My installer tells me Daikin can change boards in my units to overcome the 5 degree diff.
He’s going ahead with that for another client and will get back to me based on those results.
thanks again, great blog.
Thanks for the info. Great to hear about the board. Hopefully that will get it all going just right for you.
BTW – the Fujitsu also has the dehudification mode. I use that in spring and fall.
Thanks for the feedback. Hope to hear more from you.
Ted
Great Blog. Love it. i got the Daikin mini split ductless heatpump last week. I had many quotes for all names in the heatpump world. i chose Daikin and am satisfied. Like the above post. I too am getting a difference of temperature in one room. The electric baseboard heater themastat is reading almost 4 degrees in the difference. The remote is set at 18c and the room reads sometimes 23c on the wall mounted themastst and a handheld themastat
Also it seems the fan never stops running. (not sure how efficent this is) Even if the remote is at 16c and the room is reading 21 the fan still comes on and blows. weird..?
The manual for the Daikin lacks comsumer friendlniess.the book is pretty bleak and provides no senerios or options to maintain the system.
Im not sold that the machine running 24/7 is the best way to acheive maxium efficency
Overall im happy with the install and the product, just wish i knew a lot more about where to set the system and how to acheive the best numbers…
cheers
mark
Halifax Nova Scotia canada
Thanks Mark,
I agree, the manuals on most of these systems leave you guessing. They tell you what the buttons do and that’s about it.
I think the temperature issue is likely due to how they measure the temperature. Since they monitor the temperature of the air stream passing through the unit, there’s going to be variation dependent on the installation location. For example, in one of my rooms, I had to mount it low on the wall under some windows, so it’s picking up the cooler air that pools near the floor. In another, it’s more optimally mounted, high up on the wall, so it’s measuring the air temperature more near head height.
Most of these units have optional wired thermostats so that you can control them at a more appropriate location. I didn’t bother because I just naturally adjust them to the desired comfort level of the room rather than shooting for a given temperature. It’s not perfect, but it saves a few hundred dollars for the remote thermostat kit!
On the fan always going – this allows a much more even air circulation and hence temperature distribution. The blowers in these units are super efficient, so you’re not using much electricity with them running all the time and the comfort benefits are worth it.