Author Topic: Crawl space insulation plan - input please  (Read 399 times)

Sibley

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Crawl space insulation plan - input please
« on: May 27, 2018, 02:24:14 PM »
I need to insulate my crawl space. Specifically, reinsulate it since it has insulation which is all messed from from another project. And I don't want to mess up my house by doing it wrong! Below is specs and the plan, poke holes in it please.

Specs:
1919 house
crawl space, uneven floor, fairly ok to move around in there.
Dirt floor. NOT sealed, and its not going to be sealed. No vapor barrier currently.
Big pits in the corners so you can stand upright
Various plumbing, etc
Ventilation through 4 vents in the foundation + the door to the crawl allows some air movement.
Midwest location - real winter, hot/humid summers.
If it rains a LOT, the crawl can get water, which then drains naturally. This seems to be require unusual weather conditions. Last winter, had 3 feet of snow then it rained for a couple days and between snow melt + rain, the crawl got wet. Otherwise, appears dry.
Also last winter, the first floor was FREEZING. Which prompted the project to do something with the crawl space.

Plan:
Remove all old insulation from between joists (its installed paper side towards the ground, which I think is incorrect), general clean up of the mess
Inspect plumbing, determine if need to replace anything cause it's time before it breaks and makes a mess (1919 house...)
Install new insulation between joists, with the paper side facing the underneath of the 1st floor. This is opposite of current.
Staple up plastic as a vapor barrier on the underside of the joists
Insulate the hot/cold water pipes so maybe it doesn't take 5 minutes to get hot water upstairs in winter :)

I am most concerned with the possibility of water condensation leading to mold/rot, while also making sure that the entire first floor isn't freezing cold all winter. Based on my research, the paper side of the insulation should face the bottom of the floor, since it'll act as vapor barrier, which is the reverse of what it is currently. Would that be sufficient to keep the floor warm? Or do I need to add the plastic vapor barrier too? Would plastic cause water problems?

Also, assuming that the insulation is going to go paper side up, then how do I keep it from falling down?

TheWifeHalf

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Re: Crawl space insulation plan - input please
« Reply #1 on: May 27, 2018, 03:31:41 PM »
I can't address your questions, but in our crawl space (Ohio) the plastic vapor barrier is on the ground

TheHusbandHalf came home, info from him:
The insulation bats stay between the floor joists by friction. It's been there 26 years. Last year a couple were falling down and he said they make wires that hold up the bats. They are not attached to anything, because they are a bit longer than the space between the joists, so curve up and hold the bat up.
« Last Edit: May 27, 2018, 03:52:25 PM by TheWifeHalf »

Sibley

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Re: Crawl space insulation plan - input please
« Reply #2 on: May 27, 2018, 03:51:24 PM »
My understanding is if you put the vapor barrier on the ground, then you're basically closing the system, so you have to provide ventilation. I'm not able to do the ventilation bit, so have to come up with alternative.

TheWifeHalf

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Re: Crawl space insulation plan - input please
« Reply #3 on: May 27, 2018, 03:54:37 PM »
Yes, every spring it's my responsibility to open the vents, and in the fall to close them.

Sibley

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Re: Crawl space insulation plan - input please
« Reply #4 on: May 27, 2018, 09:26:43 PM »
Ok. My vents are fixed, they're just open. Sounds like I'm good up to the vapor barrier bit at least.

Are your bats fluffy side up or down?

bacchi

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Re: Crawl space insulation plan - input please
« Reply #5 on: May 27, 2018, 10:00:32 PM »
Use rigid foil-faced polyiso sealed on the underside of the joists. It'll add insulation and a vapor barrier and also create a thermal break that the poly barrier can't do.

Note that kraft paper batts are a fire hazard.

http://www.greenbuildingadvisor.com/blogs/dept/qa-spotlight/details-closed-crawlspace


Goldielocks

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Re: Crawl space insulation plan - input please
« Reply #6 on: May 27, 2018, 10:34:33 PM »
Vapour barrier on the warm side, in heating conditions...

I recommend spray foam insulation because of the incredible vapor seal you get and resistance to moisture.  Also would reduce any creaks.

yodella

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Re: Crawl space insulation plan - input please
« Reply #7 on: May 29, 2018, 02:29:20 PM »
So, on a related note, my husband and I also live in an old house in the Midwest and this Winter we paid to have our crawl spaces encapsulated. We do almost all other home/reno work ourselves so this was definitely a non-mustachian splurge, but it has turned out amazingly.

It made a HUGE difference in keeping the first floor warmer (floors were no longer freezing), and decreased our heating bill. Now that we are having a crazy hot few days (mid 90s) and we've had the AC on, we are not getting what I call "basementy smell" while its is running, which used to really bother me. The humidity in our basement has also gone waaaay down (our house has a basement in the middle, flanked by two crawl spaces).

I know this is totally not what you are asking about, just throwing it out there in case anyone else is thinking about it.