I’ve been getting great questions and feedback from readers, but I know many people are “shy” about participating in these public discussions. I strongly encourage you to ask anything – there’s a good chance that there are lots of other people wondering the same thing, so your questions will help others.
I choose a lot of the content that I write based on the questions I get both on and off-line. So there’s a good chance that I’ll end up writing an article inspired by your questions.
As we head into the new year, I look forward to hearing from many more of you who are helping to make Ted’s Energy Tips one of the most read energy efficiency sites on the web!
-Ted
Ted's Energy Tips 
Hi,
I’m going to insulate my home on exterior walls. I’m planing to instal 2 layers of 2″ polyiso with a foil facing. It has an R value at 7.0 to 8.0 per inch of thickness.After that, I will install verticaly wooden strips 2×1 and put on them vinyl siding.I live in New Jersey, where is mixed humid climate.I need some advice about this idea.
You’ll have some awesome insulation if you do that. The one issue to be careful of is that the foil facing is a perfect vapor retarder. If you do this, you have to be really careful that you don’t create a wall cavity that has vapor barriers on both sides of the wall because if you do that, you can trap moisture inside the walls which can rot them out.
Since you’ll have a total of four inches of poly iso, you’ll have about R-30 on the outside, which is great. The inside of your walls will then be “warm”, even if you have some fiberglass in there. In your area, you have to be careful that you don’t let the inside of the wall cavity get cold when you have that vapor barrier on the outside, again – that can lead to moisture problems. That usually occurs when people just put something like 1/2″ of iso on the outside of the house and fill the cavity with fiberglass. That allows the outer wall sheathing (that is inside the iso board) to get pretty cold, because the insulation in the wall reduces the amount of heat from the house so much.
So, to summarize:
– make sure you don’t have a vapor barrier on the inside walls
– make sure you have enough insulation on the outside to keep the inside of the walls warm (you’re doing this with 4 inches of polyiso)
Hi,
I’m interested in SEER ratings… We are thinking about a
Heat pump and the 12k btu one is 23 SEER, the 9k one is 26 SEER…. the 9K might be a little undersized, would it still be more efficient?
Matt in Seattle
Matt,
Great point. Heat pumps are strange beasts. They work by “magic” to give you excellent efficiency but they lose capacity as the temperature drops, so that has to be considered when you’re looking at the big-picture efficiency of the system.
For example, suppose that the more efficient smaller heat pump can supply all your heating needs down to 35F but the less efficient larger unit can go down to 25F (these are just made up numbers, but bear with me…)
If you live in a climate where it never gets colder than 35F, then the smaller heat pump is likely to truly be more efficient. But what if you live where I do, where you get many days in the 20’s and teens. Then, the smaller heat pump will need to be supplemented. Usually that means with an electric resistance heater. Suddenly, you’re using a lot more energy. With the larger unit, it would still be purring away without supplemental heat until it gets too cold for it to handle.
I’ve seen this situation with many central heat pumps, so I’m not just making it up. You can have the most efficient heat pump in the world, but if you have to supplement it with expensive heat whenever it gets cold, you end up spending a lot more than you would with a larger heat pump that requires less supplemental heat.