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Old 09-01-14, 02:23 AM   #1
AC_Hacker
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Default AC Insulates Under Floor of 120 Year Old Crawlspace

I have done a fairly robust job of insulating the walls of the kitchen in my house that was built on or before 1892.

But the wisdom of heat conservation trends tells me that heat loss through the floors over an unheated crawlspace can be 30%. In my case, since my kitchen walls are now 6" solid EPS & XPS, the loss is certain to be a much higher percentage.

It's now the end of August, and the thought of yet another winter with a kitchen that has an uninsulated floor is completely unappealing, so I'm giving the renovation an early start.

My son is suffering from a still sour economy, and to help him with his under employment, I've hired him as my primary mover on the project.

The first task was to clean out from under the crawl space, any refuse that got 'left' there during the last 120 years.

There were some real historical curiosities...


I'm not a car expert, but I would guess that this is a trailer (1060'?) and a Caddy (late 1960's)



Here is a tiny piece of a newspaper. I looked for a date, but no luck. My guess is any where from WWI to 1930's.



Top is a badly rusted hammer head (upholser's hammer?). I do know from historical records that the original owner was a carpenter. THis looks old enough to have been his, but it doesn't look like a carpenter's hammer.

Bottom are three bottles, some still with corks and residue. Previously, when I was digging my loop field, I found many bottles. Some were 'patent medicine' bottles, which in the time that this house was built could contain opium, sometimes even heroine. Seems it was included to relieve the ladies during their 'special days'. Since opiates cause constipation, many users of opiates also used laxatives. I have also found laxative bottles on this property. The residue could be either of these things. Interesting to note, the highest percentage of drug addiction in the US was in the late 1800's, and it was white women.


Also a medicine bottle, probably to help the men during their 'special days'.



Here is a badly decomposed hat, probably a derby, is my guess. I noticed that where the user's head came in contact with the hat, the material of the had was rotted or consumed by something



Here is a close-up of the roll of the brim... I remember seeing old flickering films of derby wearing men with brims rolled just like this. This is a Charlie Chaplin era hat... Probably dropped and lost by a workman, is my guess.



Here's a shot of actual work... 6 mil vapor barrier in place



Here's a detail of the spacers fastened to the sub floor, right next to the floor joists, to provide a 1/2" space above the foil faced EPS.

Whew!! Lotta work, lotta work to go...

Best,

-AC

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Old 09-01-14, 03:24 AM   #2
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Interesting project.

My house was also built in the 1890s and also has a crawl space, but the similarity ends there. Your crawl space is a lot more spacious than mine, and it looks like it is more open/light. The construction of yours is more modern/industrial compared to mine which is more backwoods style.

The main difference though is the floor construction above the crawl space. Is the visible boarding the underside of your floorboards? If not, what is there above that boarding?

Looking up in my crawl space you just see tree trunks rather than joists and boarding. The whole floor is solid tree trunks looking from underneath, and is floorboards when looking from the top. I have no idea what, if anything, is between the tree trunks and the floor boards. I have considered adding insulation under the flooor similar to your project but have not done so for 2 reasons. Primarily because I have been unsure of the implications as regards ventilation and inducing rot in the woodwork. Everyone I ask has different views on that and there are plenty of horror stories about people getting this wrong and causing major problems for themselves. What are your views & plans on this?

The other issue is restricting the space even further when it is difficult to move around under there already. Your insulation will (I think) be up above the joists and so will not restrict movement, but I have no joists as such and any insulation would just lower my crawlspace "ceiling". That is maybe not too important as there is rarely any need to get under there.
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Old 09-01-14, 11:45 AM   #3
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Finland? I hear excellent things about your country. I hope to visit Finland some day.

Quote:
Originally Posted by SDMCF View Post
... Is the visible boarding the underside of your floorboards? If not, what is there above that boarding?
The visible flooring is called 'sub floor', and is lumber milled with 'tongue and groove' to reduce air flow.


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I have been unsure of the implications as regards ventilation and inducing rot in the woodwork. Everyone I ask has different views on that and there are plenty of horror stories about people getting this wrong and causing major problems for themselves. What are your views & plans on this?
I am certainly not the final expert on this issue. There have been a couple of under-floor insulation projects on EcoRenovator, and I have read about and have seen photos of horror-story results, so it is with a degree of hesitation that I proceed.

The area I live in is described as having a 'maritime climate', which means that I live fairly near a very large body of water (the Pacific Ocean), and for my latitude, the seasonal temperature variations are relatively small. It also means that humidity is high most of the time except for brief periods during the summer.

So the area I live in is prone to having the kinds of problems of which you speak.

I even bought a "Mold Alert" meter (amazingly accurate) that keeps track of temperature and humidity and continuously calculates mold growing conditions, and I do have mold growing conditions most of the time.



What I have been able to find out is that when humidity-carrying air is cooled below the 'dew point', the gaseous water vapor condenses and becomes liquid water, which is when the problems start.

First line of defense is to install a vapor barrier under the house on the ground. Right now the vapor barrier does not go up the short walls, but when I am through, it will. This should reduce the continuous rise of water vapor from the ground.

My floor joists are 7.5 inches deep. My project right now is to install foil-faced Expanded Poly Styrene (EPS) directly under the subfloor. Since it is foil faced, I need some kind of air gap, so I'm going for 1/2" air gap.



I've been working with rigid foam in my house a lot, and I have struck upon the method of fitting the EPS and leaving a gap of about 1/4" all around. After the EPS is in, I will come back and fill all gaps with one-part foam, so that the EPS is effectively a single piece, with no air gaps between foam-and-foam and no gaps between foam-and-wood. I have learned that EPS can shrink over time, so I will probably return in a few years to tape the foam-to-foam seems.

Currently the R-value of my floor is about R-1.5 (bad) after the work it should be about:
  1. Floor = R-1.5
  2. Air Space = 1
  3. EPS = 9

Total = 11.5

The state I live in recommends R-30 for floors.

Next year, I will put in more, with the goal in mind to get to R-30.

My scheme is to first, reduce the humidity somewhat with vapor barrier, and then prevent the moisture carrying air from above the floor from reaching the point in the thermal gradient where it would condense.

Quote:
Originally Posted by SDMCF View Post
The other issue is restricting the space even further when it is difficult to move around under there already. Your insulation will (I think) be up above the joists and so will not restrict movement, but I have no joists as such and any insulation would just lower my crawlspace "ceiling". That is maybe not too important as there is rarely any need to get under there.
Your log construction is easy to visualize, and I have absolutely no clue as to how you could proceed, unless you totally isolated and insulated the entire space below your log floor.

And maybe some high R-value insulation above the floor.

Good luck with your project. Keep is informed as to your progress.

Best,

-AC
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Old 09-04-14, 07:54 PM   #4
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Hi AC

Why not put full 4x8 sheets across the bottom of the joists?
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Old 09-04-14, 09:11 PM   #5
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Hi AC

Why not put full 4x8 sheets across the bottom of the joists?
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Old 09-04-14, 10:50 PM   #6
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Quote:
Originally Posted by ChetT View Post
Why not put full 4x8 sheets across the bottom of the joists?
ChetT,

If I did exactly that, the air in the joist bays would self-circulate and I would lose some of the insulating potential.

My full plan is to finish this first phase, and after that, to fill the space between the joists with mineral wool, and then finish off with rigid foam, covering the bottom of the joists, exactly as you described.

Your continuous cover idea is a good one, because it will break the thermal path from the kitchen floor, through the joists.

I used to think that the thermal bridge idea was just insulation geek talk. But then I got a non-contact IR thermometer, and I could measure for myself what was happening. The insulation geeks were right. Now I'm an insulation geek, too.

Best,

-AC
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Old 09-04-14, 11:14 PM   #7
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Thanks for the response AC
I'm starting a restoration on an old farmhouse in Maine and I've stumbled across this site and from what I've read so far I expect to receive some good advice here.

The farmhouse was built by ancestors in the 1850s. It's a 3 chimney 1000 sq ft box. No insulation whatsoever. I've been in the crawl space and can see the floor timbers are 2' OC.

I asked the above question because I'm planning to insulate the floor as I described. I was planning on using 2 overlapping layers. I'm surprised to hear that a thermal current loop would form. Do you think it is a significant loss? Can it be mitigated?

Chet
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Old 09-08-14, 01:52 AM   #8
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ChetT, I would guess in Maine the code recommends R-30 for floors. That would take some thick insulation board. The way Ac is doing his is definitely one of the best ways to do this. Using a small air gap to take advantage of a radiant barrier and foam sealing the panels for a super tight fit is the way to go. Clearly its labor intensive and depending on you crawlspace height and goals for the farmhouse you might want to streamline. My 1st thought on the 8x4 sheets, it depends how big your crawl hatch is, most are tiny when you start dragging materials through it. For speed and a general improvement over no insulation I would recommend stuffing the floor with batts that fit you floor joist thickness and cover with insulation board and tape the seams. There are "fan fold" insulation panels, I've only seen 1/4", they unfold to 8x4 dimensions. Although thin, you could gain the benefit of the air sealing with less seams and tape joints
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Old 09-08-14, 02:58 AM   #9
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AC

Is there any special reason/regulation for sticking with the suspended floor?

In our house we had 2 rooms with suspended floor then the hallway and kitchen were solid concrete on soil.
We removed the suspended floors and raised the level slightly with rubble, layer or sand, damp proof membrane then insulated and heating pipes in screed.
The solid floors were dug up and constructed the same.

Steve
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Old 09-08-14, 01:37 PM   #10
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Thanks for the feedback GtoJ.
You bring up a great point that I had totally overlooked, tiny crawlspace opening. I think I have another access but now I'll need to check it out again. Duh!

I was going to post a picture of the space but I can't figure out how. When I try to insert a picture it asks me for a URL. What am I missing?

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