Man Abandons Man-Cave Because of Hidden Building Enclosure Problems
My wife and I visited family in Florida recently and our first stop was the home of my sister and brother-in-law in Lakeland (east of Tampa). They haven't lived in the house all that long, and my brother-in-law, Jack, moved his man-cave into the one upstairs room when they settled in. After one summer in the room, however, he abandoned that room for the cooler space downstairs. The problem, although not obvious to homeowners facing it, is a relatively simple one.
You can see the room in question in the photo at left. The house has a flat roof, and this room projects up through the center of it. If you have a feel for building enclosures, you may already see where this is going. If not, keep reading.
The anatomy of walls
I spotted the first potential problem when I looked out the windows in the room. I could see that the flat roof outside was above the level of my waist, which meant that the room was surrounded on all four sides with attic kneewalls more than three feet high. Knowing what I know about kneewalls, I suspected that when I looked in the attic, I'd see the typical mess there.
Yep. There it was. Insulation in a 2x4 attic kneewall with no sheathing over it. The insulation is dark in places, which indicates that air has been moving through it, too. I didn't have an infrared thermometer to measure the wall temperature, and it wasn't the hottest weather while we were there either, but I'm sure those kneewalls get pretty warm when the attic gets hot.
There's another problem showing in that photo, too. Can you see it? The photo below zooms in on it to help you out.
The floor joists below the man-cave floor allow hot attic air to go right up under that floor, so it, too, will get warm when the attic's hot.
Windows in the man-cave
Yet another problem that increases the heat gain in this room is that the two windows, one facing south and the other facing north, are the worst windows you can install. Well, OK, I guess jalousie windows, which were popular in Florida a while back, would definitely be worse, but the single-pane metal-frame windows here are a big liability in the building enclosure.
The walls have R-11 insulation (although it doesn't currently perform at the level of R-11 because of the problems mentioned above). The windows have an R-value that's less than 1. To make matters worse, the south-facing window has no overhang and gets direct solar heat gain.
A 50 year old man deserves a better man-cave
Starting from the bottom of the room, the floor has a lot of heat gain, even though it's sitting directly over conditioned space. About 40% of the wall area is attic kneewall with a lot of heat gain. The single-pane windows add more. I couldn't see the ceiling, but I'm sure it's not in good shape either.
The way to fix this room without adding more air conditioning would be to:
- Put blocking between all the floor joists and then air-seal all the way around.
- Either pull the existing insulation out of the kneewalls and spray foam insulation in its place, or install insulated sheathing over those kneeewalls and then air-seal it.
- Replace the two small windows with double-pane low-e windows.
- Insulate the ceiling, either by replacing the roof or by removing the drywall.
The first two items in that list would probably be enough to let Jack move his man-cave back upstairs. If he does all four, I have no doubt the room would be nice and comfy on even the hottest Florida days.
And wouldn't that be a nice present for someone who is turning 50 on the day this article is being published? We were there a couple of days before his birthday and surprised Jack with this banner (made by aunt, Robin Walker, an artist), a bunch of black balloons, a birthday cake, and a nice dinner out.
Happy Birthday, Jack! Let's get this room fixed for you.