Ventilation question

poirier · Tue Apr 02, 2013 7:02 pm

So this past fall I ended up insulating on the backside of the skirting. With my Dad helping me we managed to get it all done but boy what a pain crawling around under there is! Good news is it helped out big time in my mind. I had a remote thermometer down there and the lowest the temperature got all winter was like 48 degrees underneath the house! I was pretty pumped since I didn't even have to use the heat tape that I had redone.(I set up a GFI switch in the control panel so I could just switch it on if I needed to.

So that leads me to my current question if anyone can help out. We didn't do any kind of framing for the insulation we just basically wedged it between the bottom of the house and the ground. And now I need to start thinking about what I'm going to do for ventilation. I got a few ideas but I was wondering what you guys might have for ideas? I don't want to have to take any of the sheets down if possible but cutting holes for vents was my idea and then just keeping the square I cut out so I can cover it up for winter. Also if there was some formula to calculate how much I will need for vents for the square feet or something. Any ideas?

JD · Wed Apr 03, 2013 2:14 pm

It would be good to know what kind of skirting and insulation you have. You said the insulation was wedged in, so I am thinking this is insulation foam panels. You could cut your vent holes, squares of rectangles depending on the vents you are going to use, and then cut an aluminum "U" channel to trim the hole. If you have 1 1/2" foam, a 2" channel might work well. Set the trim to not only trim the hole for strength, but also hold your insulation in place. This channel would also be a secure spot to screw your vent to. You might consider blocking in the top of the foam panels with furring strips or something like that to help the panels stay in place. I am not sure about foam board sitting directly on the ground. It can deteriorate after a while and black pee ants love the stuff. I don't think they eat it, but they will tunnel around and nest in it.

A rule of thumb formula is 1 square foot or venting per 150 square feet of floor space. Keep in mind that a 12"x12" vent does not net 1 square foot of venting. You have to subtract the air restriction of the screen and vents. Or easier yet, read the cfm info on the vent's label.

poirier · Wed Apr 03, 2013 3:37 pm

Well we got a good deal on the insulation so it's between a 1 1/2" to 2" depending on the piece lol. And it is rigid pieces. I have no idea what kind of skirting I have though, sorry.

My Dad brought a roll of stuff, I think that goes under the shingles on a roof and we put sheets of that between the ground and the insulation to try and protect it somewhat. But thanks for the information about the formula that should help out.

poirier · Wed Apr 03, 2013 3:43 pm

Oh and the sheets are wedged into place and not going anywhere, we had to basically use a board and hammer them into place so it's pretty solid in there and they don't move at all. Except of course the very last piece we installed =)

Greg · Wed Apr 03, 2013 5:05 pm

I framed in a few sections that I made removable panels. I simply take the panels out and slip screen panels that I made in.

Greg

UmpJJ · Wed Apr 03, 2013 8:32 pm

My insulated skirting also needed ventilation, so I got these and have 10 of them placed around my singlewide. I used a jigsaw and easily cut the holes I needed. The "automatic" vents open and close as the outside temperature changes, and they come in various colors.

www.amazon.com/Black-Plastic-Auto-Found ... tion+vents
Or just google "foundation vents".

UmpJJ