Ask Ted!

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!


804 thoughts on “Ask Ted!

  1. Ted,
    Currently I am redoing my back addition. I have added a multi position air handler in the attic above living space, and have cathedral ceilings. The duct work is also in ceiling. I read your article about insulation between the rafters of the ceiling. Currently there are no vents on the soffits. I need to add vents? it a must to use foam board to cover insulation? Whomever built this addition made that almost impossible. Any help would be greatly appreciated. Thx, Jp

  2. Ted I just read a article of the different colors of fiberglass and what it means when it is black. Well we live in military base housing and for yrs I have said we have mold. Well we move in two days and when our movers left we noticed black mold in the laundry room! Inside our hvac system the installation is black and I called yrs ago worrying bc I’d never seen black installation. They said it was normal.

    • Mold in the laundry room usually means that the dryer isn’t venting out properly. If all that humid air isn’t going outside, it will build up in the laundry and lead to mold growth. This can be caused by clogged or damaged ducts from the dryer.
      Black insulation in ducts is quite common. Large amounts of air flow through the ducts and any dust that isn’t filtered out gets caught in the duct walls.

  3. — I have not read but about 20 of your posts and have not specifically found the exact answer I was looking for, but I am darn sure you are the right person to ask. I’m in northern Kentucky and my property was on a steep grade. I had an 18 x 52 pole building build and my floor is 2×8 connected up on 6×6 drove treated beams. I was able to get a good deal on 3 inch (recovered product) polystyrene foam and installed it between the joists. I will get under the floor and fill any cracks with expanding foam stuff (what a mess). What I do not know is if 1) I need to make that critter proof and how best to do that, and 2) do I need to install some other form of vapor barrier. The construction guy said, ‘a vapor barrier that goes on the ground;’ however, I’m unsure about that. Do I need to put OSB or some hardboard on the bottom of the joists? If you are up for consulting work, I’d love to be able to pay you for some advice. I’m building this place myself, so I’m trying to do as much work myself as I can and yet I don’t want to make terrible errors. Thanks so much. Dan

    • Hi Daniel, I thought I’d replied to your question but can’t locate the answer. So here goes!
      1) Critter protection – polystyrene is very soft and everything can chew through that. Protecting it could be challenging though. If you put wood under it, that will be exposed to ground moisture and would likely rot out. You could put sheet metal under the joists, which would also act as an absolute vapor barrier (besides the seams).
      If you did you poly, I’d attache it directly to the joists. Poly on the ground would stop much of the moisture from coming up, but then humid air that got into the gap between the ground and the joists would still have the ability to cause problems. Plus, any water from rain that got under there would just sit on the poly, evaporate and rise up into your home.
      Another option is to use foil-faced poly-iso board foam attached to the bottom of the joists. It wouldn’t have to be thick, 1/2″ would do. It would add a little insulation and protect the joists from moisture, as well as sealing out moisture very well, especially if you tape the seams with foil tape. It wouldn’t be as durable as hard metal, but could be much less expensive, easier to install, and provide a bit of a barrier from critters (though still they could chew through if determined.)

      • Ted– You are helping my wife and I move forward with confidence. Your teaching is so very appreciated. Dan and Sue

  4. Ted,
    I don’t know if you have any knowledge in this field, but based on the nature of your site and questions you have answered for me before, you may! I’m heavily redoing my house, interior and exterior. Upon doing so, I’m really tightening it up: rim joist insulation, spray foam, air sealing attic, foam board on basement walls, new windows properly flashed & sealed, etc. It will be extremely tighter than when built in the early 70’s. Anyway, in my basement I currently have a furnace, gas water heater, and gas dryer. I have a vent on the exterior that brings make up air into the cold air return of the furnace, but I do not have any vents for combustion air. This wasn’t a big deal when the house was leaky, but since I’m tightening it up I’m concerned with combustion air, back drafting, carbon monoxide, negative pressure, etc. So I’m looking for confirmation that I do probably need combustion air, and I have read about needing two vents, one high (within 12″ of ceiling) and low (within 12″ of floor), but I don’t know if this still applies. Also, I don’t know of what proximity these vents need to be to the appliances. Obviously my furnace and water heater are near each other, but not the dryer. Should I run separate vents near each?

    As always, much thanks in advance!

    • That’s a great question. In fact, energy auditor and contractors in my region a required to measure zones of the house for depressurization under a variety of conditions to ensure you don’t get backdrafting or starve these combustion devices of needed air.
      Given what you’re doing, it would be useful to get a “combustion zone analysis” to ensure things continue to run safely and efficiently.
      There are also some clever way of bringing in combustion air without essentially leaving the window open and negating all that air sealing 🙂

      • Good to know! Maybe I will drop a combustion air vent right next to the dryer. That could actually make things easier on me.
        Thanks again!

  5. a December 7, 2016, answer on the Ultimate Attic Insulation post, you discuss Roxul with air space behind and faced Polyiso under the Roxul for attic roof insulation. You mentioned you were going to attack this in a full article shortly. Have you posted this article? Could you provide a link? Regards

  6., I enjoy reading your articles. We live in a 1968 house in Calgary. We intend to remove the vinyl sidings and sheathing/plywood to remove the existing cellulose insulation, hire a company to do spray foam insulation and put the sheathing /plywood and vinyl siding back on. Is this the right thing to do? My concern is that it would affect the structure of the house when we remove the sheathing/plywood. Another option we have is to remove the vinyl sidings, install rigid foam insulation, and then put the vinyl sidings back on. We are not sure if this is a good idea to leave the old insulation material in place and because we heard rigid board could cause condensation problems. Thanks in advance for your help.

    • Thank you. I hope you read at bedtime so the articles can help you sleep 🙂
      You have a good point about structural considerations since the sheathing does provide rigidity to the walls, though I couldn’t comment authoritatively since I’m not a structural engineer. To be safe, you may wish to consult one.
      That said, you could do the job piecemeal, removing some sheathing, spray foaming, replace sheathing and moving to the next bays. Logistics could make this impractical, but it is one option.
      If you use high density spray foam, that has been shown to substantially impressive wall strength since it glues together the structure.
      On your last point, the construction with foam outside is feasible in some climates but I wouldn’t want to go that method in a cold one. As you mentioned, it could create a condensation risk. Foaming in the wall cabinets would be much safer.

  7. Ted,
    I have a persistent smell in my basement which is worse since having new vinyl siding installed on the house.
    – The main floor of the house is 50% vapor barrier and pink insulation, and 50% original 100 year old hollow lath and plaster walls.
    – The basement has no drywall or insulation currently

    The contractor wrapped the house in 1″ white polystyrene sheets sealed with red tape.
    Experiments :
    – Part of the basement footing showed higher humidity – a sheet of vapor barrier between 2 studs and a humidity meter inside shows 70% humidity constantly.
    – Another basement footing with normal humidity with the same test shows 66% humidity constantly.
    – On the main floor a hole in the lath and plaster shows 62% humidity inside.

    My suspicion is that this is a double vapor barrier problem, but I am getting conflicting advice from specialists and unsure how to proceed.

    • First question – what type of smell? Are you getting the musty smell, which almost always is indicative of moisture/mold? Or something else?
      My first thought is that the house is tighter now, so there’s less airflow up through the house, which would flush out some of the odors that you’re now smelling. Especially since the smell appears in the basement. Moisture problems in the house main floors wouldn’t be liable to cause odors in the basement.
      OTOH, I can imagine some unintended consequences of the insulation job. For example, if they added insulation to the walls that were previously open, that would impede airflow through those wall cavities. I’ve seen lots of plaster walls that are framed in such a way that the air flows from the basement all the way up to the attic. This would flush out moisture and odors from the basement. It also wastes a lot of energy, so people often want to insulate those wall cavities and end up with undesired effects.
      From your description, the fiberglass in the walls was already there and the siding contractor just added insulation to the exterior walls, behind the vinyl siding? That would definitely make the walls much tighter, so if there was natural airflow through the wall cavities and out, that would be greatly diminished. In most cases, this is beneficial – tighter house, more energy efficient. But, like noted above, the undesired consequence is that the basement may be much less ventilated, leading to moisture buildup and odors.
      The humidity levels your noting aren’t unusual for this type of year, depending on your local weather. Around here, in PA, we’ve had a fair amount of rain, so the ground is wet. That would migrate through the walls and into the cool basement, making the relative humidity high. Because of this, it’s necessary to dehumidify or water-proof the basement walls. The other thing to do is ensure that your gutters are draining properly so that you don’t get water dumped on the ground near the foundation of the house. The roof can gather thousands of gallons of water during a rainstorm. If that isn’t guided by downspouts away from the foundation, that water can saturate the dirt and cause big moisture problems inside the house.

      • Hi Ted,
        Thank-you for responding to my question.
        To me it smells like paint – the smell got worse after the siding, which I initially thought was due to the air-tightness. The pink insulation on the main floor was installed 6 years before the vinyl siding. The contractor installed new builders paper over the sheathing, followed by the 1″ polystyrene, followed by the vinyl siding. I brought him back but he said that the moisture in the footing is not caused by his work because it is all taped up properly and he followed the building codes.

        From my point of view the new codes calling for exterior insulation don’t allow for any moisture leaks at all otherwise the moisture just stays in there indefinitely.
        Previous mold inspections have not shown anything, I am waiting on results of an ERMI test to hopefully give some insight.

      • Well, I agree that I can’t see how the siding work would affect the foundation moisture, other than side-effects mentioned before. However, your contractor’s reasoning is completely wrong! I think he thinks that the only way moisture could build-up is if water got in through the siding/foam/house wrap.
        I agree with your comment about the building code. They really don’t comprehend the true nature of moisture issues.
        I’d suggest watching how the water drains next time you have a rain. Make sure the gutters are working and water isn’t pooling around the foundation.
        You might also want to actively ventilate the basement (if you have basement windows) during spells when it’s nice and dry outside. Barring that, a good dehumidifier will help. But if there’s water around the outside, you’ll be waging a losing battle because humidity will keep coming through the walls.
        You don’t have a high water table there, do you? That’s really hard to battle without seriously waterproofing the basement.

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