House is cold over the crawl space

Reply

  #1  
Old 10-06-13, 11:01 AM
S
Member
Thread Starter
Join Date: Oct 2013
Location: USA
Posts: 52
Received 0 Votes on 0 Posts
House is cold over the crawl space

This is my first autumn in a house I purchased earlier this year. It was built in 2000. Half of the main level is over a finished basement, while the other half (with the bedrooms) is over a crawl space. Photo of the crawl space:

Name:  crawl-space.jpg
Views: 5906
Size:  39.7 KB

The crawl space is vented, though I have both vents plugged.

The walls of the foundation are insulated and there is a vapor barrier over the dirt (it was installed as part of a radon mitigation system that was put in right before I bought the house). The floors are not insulated. All of the windows in the house are thermal pane.

I have central heating (high-efficiency propane). The problem is that the part of the house over the crawl space doesn't hold heat as well as the part over the basement. Our thermostat is in the part over the basement, so while it might be 70 degrees in that part of the house, the other is a few degrees cooler.

I live in Montana, so the winters can be quite cold and the summers rather warm.

Is there anything I can do to improve heat retention in the portion over the crawl space? I have read conflicting info on whether or not it's appropriate to insulate the floors AND insulate the foundation walls.

I very much appreciate any insight.
 
  #2  
Old 10-06-13, 12:48 PM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Dec 2005
Location: USA
Posts: 39,965
Received 6 Votes on 6 Posts
Welcome to the forums! Insulating the floor would be the first thing I would do. Why is there no insulation wrap around the supply ductwork? That is quite odd, even for 2000 installation. You are losing your heat/cool at a rapid rate through those uninsulated pipes.
 
  #3  
Old 10-06-13, 03:07 PM
S
Member
Thread Starter
Join Date: Oct 2013
Location: USA
Posts: 52
Received 0 Votes on 0 Posts
Hi Chandler, thanks for the response. A few questions:

1. I have heard that one ought not insulate the floor if the foundation walls are insulated (do one or the other, but not both). Is that true?

2. Since I have pipes and such exposed in the crawl space, would insulating the floor and/or the ductwork increase the risk of freezing down there?

3. Do you recommend I seal the foundation vents, and if so, what do I need to do to prevent any sort of moisture buildup in the crawl space?

2. What kind of insulation do you recommend for the ductwork and the floor?

As you can tell, this is all new to me. I'm starting to realize why I rented for so many years ;-)

Thanks.
 
  #4  
Old 10-06-13, 06:55 PM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Dec 2005
Location: USA
Posts: 39,965
Received 6 Votes on 6 Posts
1. If the walls are insulated, what is the R value? I think you will find it to be around R5 or possibly less depending on the thickness of the insulation. Your floors can use R 19 with ease and possibly R21 since you have Ijoists. Use faced insulation and put the paper to the warm side.

2. You can always wrap the pipes with insulation. There is enough residual heat to keep them from freezing.

3. This is an area where several of us disagree. In your part of the country it may pay to encapsulate the crawlspace and close up/seal the vents. Here in the South, we rely on cross breezes to keep mold etc. down by moving air constantly. You would probably need a dehumidifier or a vent from your HVAC system to "condition" the air. So I won't go any further.

4. (or 2.) Insulation for the floor, either Kraft faced fiberglas in R19+ or Roxul (preferred, but expensive) with no vapor barrier. As far as the ductwork, I'll have to defer that to the HVAC guys, but foil faced fiberglas duct wrap comes to mind, taped with metal tape.
 
  #5  
Old 10-06-13, 08:14 PM
S
Member
Thread Starter
Join Date: Oct 2013
Location: USA
Posts: 52
Received 0 Votes on 0 Posts
Ah yes, that last 2 should have been a 4. My math isn't great, but it's not quite that bad.

I'm also discovering that the builders put the thermostat in a bad place. It's practically in the kitchen, so it reads a warmer temperature than the living quarters. Moving it wouldn't help on the energy efficiency part, but the furnace would kick on more often and that would help keep the bedrooms warmer.

Thanks for all of this info. Perhaps I'll start with insulating the ducts and see what difference that makes.
 
  #6  
Old 10-06-13, 10:41 PM
G
Member
Join Date: Mar 2013
Location: USA
Posts: 457
Received 0 Votes on 0 Posts
Welcome to the forums!

The radon system requires more than just plastic (taped) on the dirt. The wall insulation/closing vents requires an exhaust fan to exterior/air exchange with house above. The floor will be much warmer (and retention) with new floor insulation. The best is SPF or rigid foam board (PIC) and cavity insulation to decouple joists from radiation with earth. Faced fiberglass is not required as plywood/OSB is same perm rating as asphalt-faced and is acceptable substitute.

Per your cold location- water surface drainage, closed crawl should only be for hot humid climates- keeping moist air out. The crawlspace tracks the outside air relative humidity- with or without vents. Insulating both walls, floor is fine with vents open. The foil facing serves as ignition barrier to leave exposed, but always check with local AHJ. Insulate the ducts (min. R-6 per link, I'd double that on the supply skip the returns- air seal them at joints with mastic/fiber tape first) and closed-cell pipe wrap water supply, as Chandler said. Air seal all wiring/plumbing holes through floor above first.

Montana and other links; Home Energy - Air Sealing - E3A: Exploring Energy Efficiency & Alternatives

http://www.google.com/url?sa=t&rct=j...3A3SWnjHaUQAdw

http://www.google.com/url?sa=t&rct=j...LHhPTC1i2cYivA

Redirect Notice

ei=HRRSUvKNMqSGjALiyIGgCA&usg=AFQjCNF5bZ9GtsPWa3u23ne2MHy9Aw1hjw applies to MO also.

http://www.smartvent.net/docs/crawlspacestudy.pdf

Per code; http://www.buildingscience.com/docum...ance-and-codes

Fig.7; BSI-009: New Light In Crawlspaces — Building Science Information

Gary
 
  #7  
Old 10-07-13, 08:17 AM
S
Member
Thread Starter
Join Date: Oct 2013
Location: USA
Posts: 52
Received 0 Votes on 0 Posts
Thanks Gary. WA is my native turf, so it's good to hear from someone there.

My radon mitigation system does include more than what I mentioned earlier. It pulls air from two points: below the soil barrier and below the foundation itself, and an exhaust fan pulls it all out of a dedicated vent pipe. Post-installation testing showed the system to be effective at bringing radon down to acceptable levels. Lately I've been wondering if a helpful side-effect of the system is moisture reduction in the crawl space.

The two foundation vents are closed right now because the temperatures are starting to come below freezing at night. But it seems you're saying that if I insulate the floors, I should open one of the vents? If I'm understanding your point correctly, how much ventilation would I need to prevent moisture buildup? I've heard from one contractor out here that I should keep the vents blocked during winter and open during summer, so I'm concerned about letting more cold air in the crawl space.

I appreciate your input and the links. As I've mentioned earlier, I'm hearing conflicting answers to certain questions from builders I speak with, hence my salvo of questions.
 

Last edited by skookumchuck; 10-07-13 at 09:01 AM. Reason: typos and adding a thought
  #8  
Old 10-07-13, 04:16 PM
S
Member
Thread Starter
Join Date: Oct 2013
Location: USA
Posts: 52
Received 0 Votes on 0 Posts
Interesting response to my query about duct insulation:

http://www.doityourself.com/forum/du...awl-space.html

"because the walls of the crawl space are insulated that makes the crawl a conditioned space. so insulating the duct will save you no money are heat. I might cut one supply vent down there to help heat the floor... But loosint the heat is not from the crawlspace id look up for that issue."
 
  #9  
Old 10-09-13, 04:36 PM
G
Member
Join Date: Mar 2013
Location: USA
Posts: 457
Received 0 Votes on 0 Posts
http://www.energy.wsu.edu/documents/...ces%5B1%5D.pdf

http://www.google.com/url?sa=t&rct=j...8h-zARBPIMzyaA

Depends on how much loss is at the ducts, I'd rather have more/all I could get at the room register to circulate where the people are.

Gary
 
  #10  
Old 10-09-13, 07:57 PM
S
Member
Thread Starter
Join Date: Oct 2013
Location: USA
Posts: 52
Received 0 Votes on 0 Posts
Hi Gary,

Thanks for the links. I'm travelling for work right now so I could only scan them, but that advancedenergy.org pdf caught my eye. Their research claims that in colder climates, one gets better results at mitigating upper-floor heat loss by insulating the floor than by insulating the foundation walls.

So I'm wondering, if I decide to insulate my floor, is there any harm in leaving the insulation on the foundation walls?
 
  #11  
Old 10-10-13, 10:10 AM
BridgeMan45's Avatar
Member
Join Date: Oct 2011
Location: USA
Posts: 3,194
Received 1 Vote on 1 Post
For your situation, and only after you've installed some decent floor insulation, would be to simply move the thermostat location. Someplace on an interior wall, closer to the living spaces away from the kitchen.
 
  #12  
Old 10-10-13, 01:09 PM
G
Member
Join Date: Mar 2013
Location: USA
Posts: 457
Received 0 Votes on 0 Posts
I'll wait until you read the links. BridgeMan45, wouldn't moving the thermostat leave the same problem? Supplying more/less heat will keep the same volumes, need to restrict the warmer ducts to balance the system before/after the added floor insulation, IMHO-though I'm not an HVAC expert. The added insulation will help balance. Is the basement insulated/finished?

Gary
 
  #13  
Old 10-10-13, 07:17 PM
BridgeMan45's Avatar
Member
Join Date: Oct 2011
Location: USA
Posts: 3,194
Received 1 Vote on 1 Post
I'm far from an HVAC expert myself. But logical reasoning tells me that the OP's heating system is shutting down too soon, because of the thermostat being "practically in the kitchen" which is typically a room that generates a lot of of heat from stove tops, ovens, dishwashers and even refrigerators. The thermostat doesn't know the rest of the living area is still too cold, because it "thinks" the ambient temperature telling it to shut things down is representative of the entire house. When in reality, it's just the kitchen.
 
  #14  
Old 10-11-13, 09:49 AM
G
Member
Join Date: Mar 2013
Location: USA
Posts: 457
Received 0 Votes on 0 Posts
Yes, moving the T-stat was mentioned already by the OP in post #5. I agree, it will pump more heat to the rest of the house but kit. will always be warmer than over crawl; unless- restrict supply to kit., or insulate/air seal crawl, or add more supply if not balanced system (possibly change the return to get more circulation) (IMO).

No problem leaving the insulation on the walls unless unperforated poly covered.

Gary
 
  #15  
Old 10-13-13, 06:40 PM
S
Member
Thread Starter
Join Date: Oct 2013
Location: USA
Posts: 52
Received 0 Votes on 0 Posts
I have considered moving the thermostat as a partial solution, but the underlying problem would remain: The house over the crawl space does not hold its heat as long as the other half of the house, which is over the finished (and heated) basement.

Nonetheless, everything you said is correct. It seems odd to have the thermostat in a part of the house that is warmer due to reasons other than furnace heat.

Unless there's a way to do it with which I am unfamiliar, I would think moving the thermostat would be a pain since all of the wiring would need to be run over to the new location.
 
  #16  
Old 10-13-13, 07:23 PM
BridgeMan45's Avatar
Member
Join Date: Oct 2011
Location: USA
Posts: 3,194
Received 1 Vote on 1 Post
Relocating a thermostat is a relatively simple operation. I was just a tyke when I watched my Pa move ours in the house I grew up in, and I've relocated several in the 50+ years since then.

You don't need to do anything with the existing wiring other than to splice onto the ends of each colored wire, using wiring having the same colors, and simply run the new set from that point to the new location. A fish tape will help when you come up through the hole you drilled in the flooring members, with someone standing at the hole you made in the wall at the new location, to grab the end of the fish tape (that you've taped the new wiring leads to) with a needle nose pliers. Should be just a two hour job once you've gathered all of the necessary tools and supplies, especially if you have basement and crawlspace access.

But I still think the floors over the crawl space need insulation. Plan on that job taking at least 10 times longer than the thermostat relocation.
 
  #17  
Old 10-14-13, 10:37 AM
S
Member
Thread Starter
Join Date: Oct 2013
Location: USA
Posts: 52
Received 0 Votes on 0 Posts
Thanks. I appreciate your input.

When I first started trying to figure out how to deal with the heat loss issue, insulating the crawl-space ceiling was what first came to mind. But as I mentioned earlier on, before I did anything I wanted to know how doing so might impact two things: preventing moisture buildup down there, and keeping enough heat in the crawl space to keep my pipes from freezing. I'm grateful to all who chimed in on those points.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: