Comments on: Remodeling? Here Are 7 Reasons Not to Skip the Air-Sealing!

By: Allison Bailes

Allison Bailes — Thu, 21 Jul 2011 00:55:48 +0000

Carl:
Carl: Interesting idea. I know you and Michael have been hot on this idea insulation causing problems lately, but is there evidence that it's a widespread problem? And shouldn't the remodeling contractor be looking for evidence of bulk water problems when they have the walls open?

You may be right that there's a product waiting to be developed that's going to make someone rich. I'd say, though, that it's still the guys who come in and fix problems left by other contractors who're going to keep profiting from this and similar problems.

By: Green Curmudgeon

Green Curmudgeon — Wed, 20 Jul 2011 18:24:17 +0000

On the issue of insulating
On the issue of insulating existing walls, I've been playing around with the idea of installing a rainscreen on the interior surface of the sheathing before applying the insulation. This could be something like Delta Dry, or even a house wrap stapled to the sides of the studs. I don't think that this will solve all the problems, but it could definitely help allow some of the inevitable moisture intrusion to dry out rather than soak the insulation. I think whoever comes up with the solution to this challenge may get very rich someday.

By: Allison Bailes

Allison Bailes — Mon, 18 Jul 2011 22:59:36 +0000

Mark:
Mark: Absolutely! It seems that this cannot be repeated often enough.

Carl: Great point about moisture and insulation. When you get in and make major changes in the building envelope, you definitely have to know what you're doing or you can end up with major headaches. If someone's remodeling, though, they're going to put insulation in those walls. The building inspector's going to require it. Air sealing won't help with bulk water problems, but it will help keep water vapor from getting in and condensing.

By: Green Curmudgeon

Green Curmudgeon — Mon, 18 Jul 2011 22:29:57 +0000

All good points, Allison, but
All good points, Allison, but one issue you neglected to mention is the challenge with insulating existing walls. Lots of people sell (and buy) blown in cellulose, fiberglass, and foam in closed wall cavities, and they often install it in cavities that are open from the interior that look like the photos above. This leads to you point about keeping moisture out of the walls – in an old house with no insulation, the moisture in the walls generally doesn’t pose a problem if there is no insulation. Once you insulate, then it becomes a problem. This leads to the issue that if you insulate an existing wall that doesn’t have a complete moisture barrier and well flashed windows (and what existing wall does?) then you are likely going to get bulk water into the wall cavity, and the insulation will keep it in there, likely causing mold and rot. This is less likely to happen in walls that have an air space between say, brick veneer and the sheathing, and walls with very deep roof overhangs. But if you start insulating walls that have wood siding and short or no overhangs, particularly in cold climates, you are almost guaranteed to have more problems than before you started, often creating conditions that promote mold and wood rot. I generally recommend against insulating existing walls unless you strip them from the outside and confirm that everything is properly flashed and shingle lapped to keep water out. It’s a real conundrum, because you want to insulate, but you also don’t want your house to rot away while your all comfy inside, for a while at least.

By: M. Johnson

M. Johnson — Mon, 18 Jul 2011 20:10:46 +0000

Good article, though the
Good article, though the message needs to be repeated over and over. I remember saying point #2 to a PhD and she did not accept it. In all fairness her PhD was in biology not physics or philosophy. I saw it as the Law of Conservation of Matter.