Has anyone dealt with insulating an addition (without a foundation)? The previous owner had laid batt insulation in the crawl space underneath, directly on the ground, which is obviously now a home to critters. I have ripped it out and am now looking into spray foam insulation underneath. Also wondering if I should seal up the crawl space or keep it ventilated.
We built an addition with no basement under it, there is a small space but no access, as it is about 8" off the ground, so you wouldn't be able to crawl in there anyway. We do blow hot air under there, no issues as of yet and no issue keeping warm in the winter. The reno is about 8 years old now. Only critters we have had, was some wasps, but a shot of wasp killer beside a heating register took care of that.
If there is a space between the bottom of the insulation and the top of the ground, then definitely it should be vented. Even if the ground appears to be dry, there will be moisture from the ground coming up into the unvented space and you may eventually end up with dry rot in your wood framing, and there will be that musty smell. You can put in vents that will keep the critters out.
Continuous ventilation seems like a bad idea, especially in winter. You’d have near outdoor temperature in the crawl space bridging through the floor structure.
Continuous ventilation seems like a bad idea, especially in winter. You’d have near outdoor temperature in the crawl space bridging through the floor structure.
Sorry if I wasn’t clear. I have no intention of providing mechanical ventilation.
We built an addition with no basement under it, there is a small space but no access, as it is about 8" off the ground, so you wouldn't be able to crawl in there anyway. We do blow hot air under there, no issues as of yet and no issue keeping warm in the winter. The reno is about 8 years old now. Only critters we have had, was some wasps, but a shot of wasp killer beside a heating register took care of that.
Sorry if I wasn’t clear. I have no intention of providing mechanical ventilation.
Intermittent mechanical ventilation could probably be better though than a passive setup like vented soffit. With vented soffit that space would be as cold as your attic in the winter.
Continuous ventilation seems like a bad idea, especially in winter. You’d have near outdoor temperature in the crawl space bridging through the floor structure.
I have an insulated crawl space under my house (it's on steel piles and has insulated skirting around the perimeter, with a 6 mil vapour barrier on the ground). The floor is very well insulated and is warm even on the coldest days of winter. The vents in the insulated skirting are the automatic type which close when the outside temperature gets cold. So, the space is vented during the spring, summer and fall, and on warm days during the winter and not vented when it is cold outside.
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Intermittent mechanical ventilation could probably be better though than a passive setup like vented soffit. With vented soffit that space would be as cold as your attic in the winter.
Yeah the whole thing is far from an ideal situation. It was cold this winter for sure.
Quote:
Originally Posted by Shin Pad
I have an insulated crawl space under my house (it's on steel piles and has insulated skirting around the perimeter, with a 6 mil vapour barrier on the ground). The floor is very well insulated and is warm even on the coldest days of winter. The vents in the insulated skirting are the automatic type which close when the outside temperature gets cold. So, the space is vented during the spring, summer and fall, and on warm days during the winter and not vented when it is cold outside.
I have an insulated crawl space under my house (it's on steel piles and has insulated skirting around the perimeter, with a 6 mil vapour barrier on the ground). The floor is very well insulated and is warm even on the coldest days of winter. The vents in the insulated skirting are the automatic type which close when the outside temperature gets cold. So, the space is vented during the spring, summer and fall, and on warm days during the winter and not vented when it is cold outside.
Aside from a heated crawl space that’s definitely the way to do it. Do you know any model information on the vents?
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Has anyone dealt with insulating an addition (without a foundation)? The previous owner had laid batt insulation in the crawl space underneath, directly on the ground, which is obviously now a home to critters. I have ripped it out and am now looking into spray foam insulation underneath. Also wondering if I should seal up the crawl space or keep it ventilated.
If I understand your situation correctly heres what i recommend;
Spray foam the entire underside of the addition, this becomes your insulation and vapor barrier for the warm side.
Use a heavy gauge poly (10 mil), sealed to the outside walls, to create a barrier between the soil and the space. You could leave the wood on top as a physical barrier. This should keep the area from getting musty and moldy.
Seal off the walls and install a couple vents like Shinpad posted to allow air movement to keep the area from accumulating moisture. Same principal as venting an attic.
2 rats in 2 days in the trap. The 2 of them were pretty bold, strutting around outside. So I think that problem is taken care of now. Now to get going on the insulation. Thanks for all the tips.
2 rats in 2 days in the trap. The 2 of them were pretty bold, strutting around outside. So I think that problem is taken care of now. Now to get going on the insulation. Thanks for all the tips.
Is there a way to seal it from the bottom before using any spray foam so it's basically sealed from the dirt? Maybe put some soffit to the underside of the beams.
My experience with mice here in Calgary is that they will chew through things for heat. I wouldn't be surprised if critters would chew into the foam and make an even nicer and more durable nest for themselves.
Many years ago a neighbour of mine built a wood enclosure for his garbage cans. It sat on two concrete blocks.
The mice chewed through a tiny space between the 2 x 4's on the base and were having a party inside when he found them.
I have a few good mice stories. One time I left a Glad bag of clothes outside our front door for donation. They didn't come to pick them up after a couple days, so I decided to drop them off at Goodwill instead. I put the bag in my van and noticed there was a tiny tear in it. Of course a split second later a mouse pokes his head out of it, I froze because it startled me, then jumped out of the bag and into my van.
After about 12 hours of ripping everything out the van, seats and all, I was convinced it was still in there. So, I loaded it up with about $15 of traps and glue traps and closed the doors. About 10 minutes later I looked inside, and it was stuck to a glue trap underneath the drivers seat. Thank God I got him so soon otherwise I would have had to sell the van.
Is there a way to seal it from the bottom before using any spray foam so it's basically sealed from the dirt? Maybe put some soffit to the underside of the beams.
I feel like that actually creates a more desirable critter home.
If it’s poly on the ground -> vented air space -> uncovered spray foam, they won’t really have anywhere to nest. With soffit down at the beams, they could nest between the soffit and spray foam.
I’d make sure I had an access hatch and a couple pouches of poison in there as well.
I have metal flashing at the bottom of my skirting, which extends out horizontally a few inches below the ground surface, which stops mice from getting into the crawl space. Living in the country, mice are a problem if you don't take the proper precautions. I also put a bit of poison laced grain (used for killing mice, gophers, etc ), around the perimeter, over top of the polyethylene sheet, as an added precaution. This is a new home, which we just moved into in September. So, although I don't use the crawl space at all, I do check it once in a while to ensure there aren't any mice in it. So far, there has been no sign of mice.
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It's all ice right now so I can chip away at it, but I think this is the first year it's ever been an issue. I think the constant freeze/thaw Ive seen this year is likely the culprit but luckily I think it's at peak now as we are heading into April I don't expect a lot more new water there and there is very little snow on the roof that would go down through the downspouts
