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Insulating Crawl Space - Quick Advice Needed
Old 10-25-2008, 02:09 PM   #1
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Insulating Crawl Space - Quick Advice Needed

I had been planning to insulate the foundation walls of my crawl space to keep my pipes from losing heat and to protect against them freezing if I ran my wood stove and the zone pumps stopped circulating.

I picked up 14 R10 sytrofoam 2 inch thick panels and had planned to attach them tomorrow.

SamClem pointed me to a Dept of Energy web site and I saw a footnote that warned not to insulate the walls of a ventilated crawl space. This made me start to worry that I would be building up moisture if I put the foam panels on the walls and also had under-floor insulation.

At this point I think I am going to cancel the plan to insulate the walls and attempt to build some sort of additional insulation around the pipes themselves.

The pipes have the black foam jackets that are slit and placed around the pipe. One pipe has foam that is very brittle - does this mean that it is worn out and should be replaced?

I am thinking that I will try to use some of the styrofoam to make a block around the pipes a couple inches thick or more and maybe hold it in place with wire that I wrap around and twist.

I live in CT, so I am listed as zone 1 on the insulation charts.

While I was under there I noticed that the current setup is R19 six inch batt insulation between the joists. However, the kraft paper vaper barrier is on the bottom facing the crawl space rather than on the top directly against the floor of the living area. In addition the entire bottom of the insulation is covered by clear plastic sheets.

I also discovered that the dryer hose is venting into the crawl space. I will be fixing that today or tomorrow. I think it has been like this about six years. When I had the new siding the contractor installed a four inch vent in the wall above the crawl space but the hose did not reach. I think I was supposed to add hose but forgot about it.

When I look up at the existing insulation there are several sections that seem to be definitely wet. In some of these the kraft paper is torn or missing. I think that this may be due to mice living in the insulation since the way it is set up the clear plastic and kraft paper make a nice floor for their little house.

Am I correct in assuming that the insulation is installed backwards?

Most of what I see says the if you live in a cold area the vapor barrier should be directly against the interior floor. It would only be in the deep south or in a very wet area that you would have a vapor barrier below the insulation.

I am thinking that I should reverse the insulation so that the vapor barrier is on the top against the floor.

It would seem that I definitely need to pull down any that seem to be really moist and replace them.

I am thinking that I will hold the insulation up with chicken wire stapled to the joists or maybe with some wire run in a zig zag pattern.

At this point I am pretty sure that I am not going to install the foam panels tomorrow, but any advice or reassurance will be appreciated as always.

Thanks. I don't know how I would be able to deal with this without all the help I am getting from this group.

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Old 10-25-2008, 02:28 PM   #2
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I've insulated a crawl space in the past. To deal with moisture, I installed plastic over the dirt flooring and lapped it up the walls to make a semi tight seal. The crawlspace had vents and I set up the insulation so it could be removed in the vent area in the summer when the vents were open, and installed over the vents in the winter. I insulated the walls with R13 fiberglass, though foam should be find.

You are correct that the vapor barrier should have been installed on warm side of the insulation, just below the floor. I'm not sure it is worth it to pull it all out and flip it, though it is certainly the most correct way to install it.

You probably mean principal not principle. Judgment only has one "e".
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Old 10-25-2008, 02:35 PM   #3
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travelover - Did you have both insulation on the crawlspace walls and on the floor of the occupied area?

I may not have mentioned it, but I have black plastic over the entire dirt floor of the crawl space. That made a big difference when I installed it a few years ago. Much nicer going under there now.

I need to get some more plastic and take care of the edges better.
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Old 10-25-2008, 02:46 PM   #4
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floors we have had insulated the pros use a nylon cord stapled up to the floor joist bottoms - it's stretchy, so makes for a nice tight run.wet insulation makes me think leaky drains or tub overflows or supply line leaks. See TAls posts - floor insulation is upside down, but flipping it is nasty work - maybe do a run or so and decide then. they also make stiff wires that you push up between the joist and then the pressure of them being a bit long holds them and the insulation in place. Only good if your floor joists are regularly spaced - all our old places were too random for them to work.
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Old 10-25-2008, 03:31 PM   #5
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Originally Posted by joesxm View Post
travelover - Did you have both insulation on the crawlspace walls and on the floor of the occupied area?
There was some thin, old insulation under the floor, falling apart. I just left it alone. After I insulated the crawlspace walls, the floor was MUCH warmer in the winter.

I may not have mentioned it, but I have black plastic over the entire dirt floor of the crawl space. That made a big difference when I installed it a few years ago. Much nicer going under there now.

I need to get some more plastic and take care of the edges better.
Unless you have special issues, moisture shouldn't be an issue. As you mentioned, plastic sure makes in nicer to crawl on.
You probably mean principal not principle. Judgment only has one "e".
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Old 10-25-2008, 04:16 PM   #6
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- Insulating the pipes won't stop them from freezing--insulation only slows rhe transfer of heat, it won't add warmth to the pipes. What you are trying to do is keep the water in them above 32 deg F by allowing the heat from your home to warm the crawlspace. If the floor of your home is well insulated, you won't be getting much heat added to the environment down there, and the likelihood of pipe freezeup is increased.
- The DOE site probably recommends against insulating the walls of a ventilated crawlspace only because it doesn't accomplish anything. If you are encouraging gobs of outside (10 deg F) air to enter the crawlspace, there's not much sense in insulating the walls of that crawlspace.

To keep the pipes from freezing and keep your floor warmer, you have two options:
1) Insulate the pipes AND add electric heat tapes to them. These turn on when the temps get below approx 40 deg F. Then, repair and improve the insulation under your floor. Leave the vents of your foundation open. This will work fine until the heat tapes stop working (and they will someday), then your pipes will freeze and burst unless you are really lucky.
2) Warm the crawlspace. You'll be making what is technically known as a "conditioned crawlspace." Do this by blocking off your vents, insulating your foundation walls as you'd planned to do, and removing the wet/damaged insulation from beneath your floor. You need to remove enough insulation to let the crawlspace warm from the heat of your floor. If you leave any in place (maybe under a bathroom or another spot you'd especially like to keep the floor as close to the temps of the inside as possible), you should perforate any vapor barrier that is either above or below the insulation against the floor. Just because I'm the cautious type, if I did this, I would probably add heat tapes to the pipes anyway, just as a backup (in case the night gets REALLY cold and the crawlspace happens to drop below freezing). If you want, you could instal a cheap electronic thermometer in the crawlspace so you can see how cold it gets this winter before installing the heat tapes/insulation. Don't worry about heat loss through the soil underneath the crawlspace--it will be warmed by the house, too, and it will probably never get below freezing due to the influence of the warm soil down low. (if you go down probably 48" in your area, the soil never gets cold enough to freeze. By insulating the walls of the crawlspace, the steady-state year-round temps of the soil will get very close to the surface and help keep the crawlspace warm).

Whichever route you choose, definitely add plastic all over the crawlspace "floor", and lap it about a foot up the walls. Put it under the styrofoam (assuming you insulate the walls).
Insulated, unventilated crawlspaces are relatively new, and some of the traditionalists don't like them. Here's the science behind the idea.

Building Science Corp--PDF on Conditioned Crawlspaces"

It reads, in part:
Crawl space venting is generally viewed as good practice despite the obvious moisture problems that occur when
outside air with a dew point higher than interior crawl space surface temperature is permitted to enter a crawl space.
Unvented, conditioned crawl spaces with insulation on the perimeter solve this problem. Unvented, conditioned
crawl spaces with insulation on the perimeter perform better in terms of safety and health (pest control), comfort
(warm floors, uniform temperatures), durability (moisture) and energy consumption than passively vented crawl
spaces with sub floor insulation.
Perimeter insulation rather than floor insulation performs better in all climates from an energy conservation
perspective. The crawl space temperatures, dew points and relative humidities track that of the house. Crawl spaces
insulated on the perimeter are warmer and drier than crawl spaces insulated between the crawl space and the house.
Cold surfaces that can condense water are minimized when crawl spaces are conditioned.
Wintertime ventilation makes crawl spaces colder and increases the heat loss from the home – venting crawl spaces
wastes energy, and can lead to freezing pipes and uncomfortable floors.
P.S. (Added later) I notice that the BSC document recommends including the crawlspace in the heating/cooling envelope of your home by actively facilitating airflow. This could be done simply by adding an opening in an existing duct if they run under your floor, then adding a return air mechanism to alow the air from te crawlspace to either re-enter your home someplace or to re-enter your HVAC system through the return air system. Or, just add a small fan that moves air from the house into the crawlspace and either back into the house (preferable from an energy conservation standpoint) or outside (not so good). See the drawings on pgs 3-4 of the document. The way that would probably lead to the least energy use and most comfort is the one labeled "C". The air from the crawlspace is drawn into your furnace when it turns on, and make-up air flows passivelu from your house through a grill or two into the crawlspace. This method has the advantage of not forcing the cooler crawlspace air into any of the rooms of your house--it goes into the furnace.
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Old 10-25-2008, 06:14 PM   #7
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The conditioned crawlspace looks interesting, but I don't think I can accomplish that this year. I would be afraid of doing it without the active air transfer because I have pretty high water table and would worry about being able to keep it truly dry.

I did buy the remote thermometer and humidity sensor so I will be able to monitor the conditions closely.

I picked up some 4ml plastic (I was too cheap to shell out $26 for 6ml) and will do as much as possible to really seal the ground. It would have been nice to have the foam panels to hold the plastic to the wall, but I will figure something else out. I have some left over wood, so I probably will put it next to the plastic against the wall and drive some long left over spikes into the ground to hold the board against the wall. I will try to seal the spike hole with duct tape.

I got some dryer vent tubing, elbow and clamps so I hope I can manage to fix the dryer vent tomorrow (raining now).

Although I like to vent the space in the rest of the year, I have covered the vent opening in previous winters and will do so again. That should at least protect from heavy winds blowing in.

I may end up running on oil only when it is really cold so that I do not risk freezing the pipes. I have been like this for 20 years and have not had them freeze yet. Maybe the screwed up floor insulation is helping to keep the space warm.

I may also look at having the oil hot water pipes flushed and re-filled with anti-freeze. I think I have anti-freeze now, but the HVAC guy that fixes the A/C at work said that after 18 years it would be good to flush the system.

I think I will deal with the obviously wet sections of insulation but not make a big project this week.

Home Depot said that I had 90 days to return the foam panels as long as they were not damaged.

I think it I bail out of the crawl space project this season and focus on fixing the attic insulation it will give me time to think things over.

I am definitely going to try to somehow re-use the old attic insulation. My next door neighbor was saying that he also did not have enough insulation and they seem to be on a tigher budget. I suppose if I can re-furbish the old insulation enough and still feel that I want new stuff I can see if he wants me to bring some over for his attic.

Sorry for so many panic stricken questions.
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Old 10-26-2008, 10:50 PM   #8
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I gave up on insulating the walls today and took all but two of the foam panels back to Home Depot. I saved two to try to make a hatch cap for the attic hatch.

We crawled under and managed to connect the dryer hose to the outside vent. It wasn't too bad. We supported it from the joists with wire and staples and put a nail into the wall on the outside end to anchor it to the outside vent.

It was nice to see the air blowing out where it should and I am sure that the crawl space will be that much better off without the moisture.

The only thing I miss is the opportunity to run the dryer to heat the crawl space in a freezing emergency (assuming I still have power). I am toying with the idea of cutting a second dryer hole so I could switch the hose and run the dryer with no clothes in it as a heat source, but that will be later on.

I got some more plastic and will try to do a better job of covering the dirt. I noticed that my previous work had some weak spots and I think that the contractors messed up some when they were under it a few years ago.

I gave a lot of thought to the concept of the conditioned crawl space. I think I may consider that for next year's project. With that in mind I am going to hold off on any major crawl space floor insulation replacement. I will pull down the several really wet looking sections and probably replace or maybe just leave without so some heat can leak in. I will be blocking the vent openings for the winter.

I figure that I will get more bang for the buck on the attic insulation and given my track record of half-finished projects it will be best to focus most of my energy on completing the attic.

I hadn't mentioned it, but another of my previous request for advice threads involved my old stove conking out. The exhaust hood fan also broke.

Two weeks ago I got the new hood and with much difficulty step-father and I extracted the old one (which had been cemented to the wal with tile grout in some portion) and installed the new one.

As luck would have it, the baffle that was supposed to divert air to the duct instead of to the interior charcoal filter mode was leaking air and the outside vent flap was not opening up.

We did the "space walk" today and improved the baffle with some trusty duct tape. I also noticed that the exhaust flap inside the hood was sticking and picked off some sticky stuff with needle-nose pliers. Things seem to be working pretty well now.

The old stove had an oven heating element blow out, so I have not had an oven for several years. It was suggested that if I could go so long without an oven I had better not spend a lot on a new stove since obviously it was not that important to me.

I would fix the old one, but it is over 20 years old and the top is pretty disgusting looking with a lot of baked on crud from pots boiling over.

I have my eye on a nice white GE that matches my new white hood. This is a simple model with a glass top - two 6 inch, one 8 inch and one 12 inch burner and self cleaning oven but not much more. I think I will put the order in this week.

Well that is the report from the front lines for the moment.

Here's hoping that this coming week in the market will at least be level.

With all that I am spending on all these projects I am a one man stimulus package :-)
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Old 10-28-2008, 01:15 PM   #9
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Originally Posted by travelover View Post
The crawlspace had vents and I set up the insulation so it could be removed in the vent area in the summer when the vents were open ...
Conventional wisdom has always been to open vents in the summer.
But here in the hot humid southland I've found that this makes my
crawlspace (under-floor insulation, none on crawlspace walls) very
very humid - like, droplets of water on the undersides of the floor
batts and furnace ductwork, very scary.

So I now keep my crawlspace vents closed ALL the time, summer and
winter alike. Of course, I also completely covered the crawlspace
dirt floor with plastic when I did this (I went to a spcialty building
materials place and bought something like 10mil; I figure with all the
labor involved, why not use the best possible materials, I don't want
to ever have to do this again !).

It's pretty dry down there now.

But I am tempted to also insulate the foundation walls. I guess if I do
this, I should remove the under-floor batts, as samclem recommends.
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Old 10-28-2008, 08:53 PM   #10
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I bought 4mil plastic to beef up the dirt covering, but now that you mention it I probably should use 6mil even though it costs $26 compared to $13.

I may go buy some more and either return the 4mil or just keep it for some other purpose in the future.

Like duct tape you can never have too much plastic sheeting.

On another note, I made two returns to Home Depot Sunday and yesterday. They credited my charge card, but while I can see the additional purchases I made those days, the credit is not showing up on my card account.

I am assuming that they delay the credits for review or to float the money. Has anyone had a similar experience or gotten stiffed by Home Depot on return credits?

I also noticed that the appliance store charged the card for my stove but it will not be delivered until next Sunday.

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