Interior Insulation With Rigid Foam

Rigid foam insulation is the best thing since sliced bread. It’s thin, effective, has a great r-value and acts as a vapor barrier. With the time and space saved, it’s worth its weight in…well, rigid foam. It’s sort of expensive though at $18.99 per 4’x8′ 1 inch thick sheet. But the mice hate it and once it’s installed, it’s good for life. That’s why I’m using it to insulate the log cabin room.

I gave you a sneak peek of the one finished wall in my window installation post, but now that this phase of the project has begun, I’m going to be talking about insulation a lot more.

Okay – where to begin. When this past Winter rolled around, we felt a distinct chill in the air. We felt drafts and cold walls. Laura and I had conversation upon conversation about why the house was so cold. After locating and fixing some of the larger problem areas, I decided to start methodically tackling the lack of proper insulation in this house. She kept asking me, “Why don’t people insulate correctly in the first place?” I replied, “Because houses get built in the Summer. Insulation is one of the last things people think about when they are sweating. Also, builders have a tough time reconciling the fact that Winter will return. When they build, it’s 80 degrees out.”

I know that doesn’t make too much sense when reading it, but it’s true. Even me – the insulation nut, has mostly forgotten about the cold now that’s it’s late Spring. I have to kick myself to recall waking up to a house that’s 30 degrees on the inside. My plan is to stop that from occurring, because as they say in book 1 of “Game of Thrones” (which I’m reading at the moment), “Winter is coming.”

In the log cabin room, I felt moving air during the cold months. The room is constructed with 6 inch thick logs, one stacked on top of the other. For the peaks and the roof, it’s stick built. Since the walls are solid, they are not insulated. At an r-value of 1.5 per inch of solid wood, the walls currently have an r-value of 9. That’s far below what’s recommended. Not that I know what’s recommended, but I can imagine having walls with an r-value of 9 is low. The ceiling is insulated with r-19 insulation. That’s also low (I can imagine). But really, the issue in the room isn’t low r-value – it’s draft. The room isn’t sealed. There are hairline gaps and checking in the wood that the walls are constructed of and the roof has a ridge vent that warm air is finding its way through. A layer of plastic all over the interior of the room would work wonders, but I’m going to step it up a notch.

When I touched the walls of the log cabin room over the Winter, they were cold. But while they were cold, they weren’t freezing cold. That solid wood was doing a decent job of insulating the room. I attribute the cold and draft to the ceiling and the windows. As you know, the windows are now installed and sealed.

I got the idea of installing rigid foam to the interior of this room a while back, after learning about insulation ad nauseum. And when I say ad nauseum, I mean ad nauseum. Much of my Winter months were consumed with me reading articles about how insulation works. And after all that reading, I made the decision to go with rigid foam. Here’s why: with foam insulation, the room gets sealed from air flow. The room also gets a vapor barrier. A vapor barrier is very important because I’m pretty sure no one wants to see water leaking out from the interior of their walls.

Do you know how water condensation works when it comes to insulation? No? Well, let me fill you in. When warm, moist air comes in contact with cold, dry air, condensation occurs. More specifically, condensation occurs right at the point of contact. Say you have fiberglass insulation installed in a wall with no vapor barrier. One side of the insulation is cold from the outside air and the other side is warm from the inside air. In this case, somewhere in the middle of that insulation is going to be the point of contact for those two temperatures and moisture levels. When the air collides, you get condensation and puddles. Or, you get sopping wet fiberglass insulation in your walls.

Back when we lived in Pine Bush, NY, we had a house where the corners of a few rooms weren’t insulated. Common problem caused by lazy builders. I can remember trying to paint those rooms in the middle of Winter and having the paint run down the walls and not drying properly. The issue was that those sections of wall were freezing and condensation was forming in the interior of the house. The sheetrock was the vapor barrier. That’s why insulation and the proper r-value is important.

Okay, enough of the lesson. Let’s get to some pictures of what I’ve done so far in the log cabin room. My basic plan is to skin the room with 1 inch thick rigid foam insulation. This will give the entire room a boost of 5 r-value points. This room had no issues with condensation and the temperature dropped to -24 this past season. Like I said above, I’m mostly concerned with drafts.

I’m taping all the seams and I’m going to inject foam in all the gaps that are left exposed after the install is completed. I think it’ll be great.

A few days ago, I picked up this really great tool. It’s an adjustable t-square. I was going to go with the fixed one, but Laura persuaded me to get the adjustable one, just in case. Well, I used the adjustable part yesterday to find the angle of the peak in this particular room and wow, just look at the results.

I’m not sure I’ve ever cut an angle of anything so perfectly. Here are a few pictures of the t-square. The 4 foot length is also especially handy for cutting long strips of insulation like this.

I’ll take more pictures of this part of the project as I go along. I know how exciting it is for all of you!