heating crawl space with heat pump

Closed Thread

  #1  
Old 10-25-08, 04:06 PM
D
Member
Thread Starter
Join Date: Jul 2008
Posts: 16
Received 0 Votes on 0 Posts
Question heating crawl space with heat pump

We have been heating the crawl space in our house for several winters because the ductwork was all torn up from rats. Cockroaches and waterbugs coming in through the vents was my big clue there. Of course all that heat was lost because of the ridiculous number of vents in our foundation.

I thought of a way to prevent the nasty smell been coming through the vents, keep the cockroaches and rats out, and heat the house without having to go down and repair the ductwork, all at the same time: seal up the foundation vents with insulation and replace the thermostat with a remote bulb thermostat locating the sensor under the house. I'll just run the heat pump through the leaky ductwork and heat the crawl space. The hot air will rise and heat the floor from beneath, a DIY form of radiant floor heating.

Has anyone done this and can anyone give me a reason why I shouldn't do this? Radiant floor heat web sites are mysteriously silent on this simple and cheap modification of pre-exisiting systems to accomplish the same goal. Warmup.com mentions that it was the original design of radiant floor heat systems by the Romans.

I've already had a few HVAC vendors give me some specious arguments about moisture buildup, another even told me he'd "lose his license" if he touched the job. I'd like to get some second opinions. Anyone? thanks in advance.

Dave
 
Sponsored Links
  #2  
Old 10-25-08, 05:09 PM
airman.1994's Avatar
Member
Join Date: Dec 2005
Location: VA
Posts: 5,795
Received 8 Votes on 8 Posts
No way would I do that unless you have a sealed crawl space. You will be bringing in all the dirt, bugs, mold, fiberglass. Id fix the duct work before you have all of those IAQ night mares coming into your home.
 
  #3  
Old 10-25-08, 05:22 PM
D
Member
Thread Starter
Join Date: Jul 2008
Posts: 16
Received 0 Votes on 0 Posts
oh right, I forgot that important detail (the one I just described is basically what we've been living with for two years). I'd also seal up the floor vents. Only the crawlspace would be forced air heated, the floors of the house then be convectively heated by the hot air under the house. What about now? Also, what does IAQ stand for?
 
  #4  
Old 10-25-08, 08:42 PM
airman.1994's Avatar
Member
Join Date: Dec 2005
Location: VA
Posts: 5,795
Received 8 Votes on 8 Posts
Only way this will work and be safe for IAQ Indoor Air Quality is to remove fiber glass insulation. Remove duct work, insulate walls and floor with 2in foam board, lay at least 6 mil vb on top of foam board. If you have a fossil fuel furnace you will still have to have combustion air, also if your furnace and AC or sized correctly they will be under sized when you do this.
 
  #5  
Old 10-25-08, 08:52 PM
D
Member
Thread Starter
Join Date: Jul 2008
Posts: 16
Received 0 Votes on 0 Posts
heat pump too small?

The heat pump is outside and it's about double sized for our house (the previous owner installed it). One of my primary concerns is that the heat pump will be short cycling because of the much smaller air space we are asking it to heat. I don't want to run it for long though, natural gas is damned expensive so that'll work as long as it doesn't turn on/off too frequently.

Sorry airman, I don't follow your logic at all. First of all, the hot air will only circulate in the crawl space which is under the floor. I read somewhere else that it is NOT advisable to put vb and insulation on the floor since that'll prevent water vapor from escaping. As far as getting rid of insulation, the floor vents will be blocked off so none of the air will get in the living space. The concept here is a variation of radiant heating: The crawl space hot air will rise and heat the floor from below... seems like a simple enough concept to me but for the life of me, I've gotten completely perturbing answers from wherever I've posted this. It seems that most Americans are very much limited to the box of how things are done by HVAC manufacturers and no room left for some creative problem solving. Thanks for trying.
 
  #6  
Old 10-26-08, 05:19 AM
airman.1994's Avatar
Member
Join Date: Dec 2005
Location: VA
Posts: 5,795
Received 8 Votes on 8 Posts
If you don't seal the crawl space all the humidity from the earth earth will get into the crawl and you will have moisture problems. This is what the VB and insulation or for. I don't know where you read that at but it is very wrong. If you seal were the vents are in the floor you will have no place for the heat to go and your Heat pump will be way over sized which will kill the unit in short time. It will also be way less efficient. What about cooling you will not be able to cool your home! Also to heat the floor you will have to heat the crawl to a high temp. 72 degrees is not going to heat the floor. I don't know the formula but my guess is at least 90 degrees. The reason you or getting answers you don't like is it will not work. I guess you are trying to find somebody that agrees with you so you will fill better about this so you can do it.
 
  #7  
Old 10-26-08, 12:05 PM
D
Member
Thread Starter
Join Date: Jul 2008
Posts: 16
Received 0 Votes on 0 Posts
heating/cooling crawl space w/ heat pump

Airman, In your prev. post, you made reference to Indoor Air Quality and an undersized furnace, hence my misgivings. You now seem to understand the idea I am putting forth, so I'll respond to that. And it is true, I am not easily dissuaded. The responses have to be well reasoned and I am not susceptible to fear mongering at all. I have a physics degree and have done off beat things like this before, some of which worked fine despite all the naysaying.

I read about not using vapor barrier at:

http://www.extremehowto.com/xh/artic...ticle_id=60576

I plan to use a thermostat with a remote sensor placed in the crawl space in the vicinity of the return duct on the heat pump. When it reaches 80 degrees, it shuts off. The only concern i have there is short cycling, but it if the heat pump dies in a few years, I'll know by then that I can replace it with a much smaller unit (even smaller than recommended for this size house), if this idea works. We have no insulation in the floor and the floorboards are thin in this older N. Carolina home, so I think 80 degrees in the crawl space should be adequate (It'll be better than we've been used to anyways which is to freeze our a**es off in the winter!).

Cooling can be done the same way. Last summer as a little experiment, I sealed off the larger sized openings in the foundation with heavily insulated hatches. We were able to stay cool just from the cool floor (which I knew was being accomplished by all the duct leakage). An HVAC guy recently inspected it and confirmed my worst fears: two 14" ducts had detached from the main duct and were laying on the ground. We've only got one floor vent that works well, and I long suspected it of spreading a nasty odor as it circulates the dirt and filth from the crawl space into the living space.

If this idea doesn't work, or is too inefficient as you suggest, I will switch things over to hydroponic radiant heat. Forced air doesn't work for our home anyways because of the high ceilings. All the hot air collects in my bedroom on the 2nd floor and the 1st floor stays cold.
 
  #8  
Old 10-26-08, 12:40 PM
B
Member
Join Date: Aug 2007
Location: Northwest Arkansas
Posts: 20
Received 0 Votes on 0 Posts
Originally Posted by djsmith9 View Post
oh right, I forgot that important detail (the one I just described is basically what we've been living with for two years). I'd also seal up the floor vents. Only the crawlspace would be forced air heated, the floors of the house then be convectively heated by the hot air under the house. What about now? Also, what does IAQ stand for?

Extremely BAD idea in so many ways, I don't know where to start.

You will never achieve what you hope to by doing what your thinking of doing. Scrap this idea and move on.
 
  #9  
Old 10-26-08, 01:10 PM
D
Member
Thread Starter
Join Date: Jul 2008
Posts: 16
Received 0 Votes on 0 Posts
This is your second post in over a year and I'm the unlucky recipient? What'd I do to deserve this besides have a great idea that won't make some HVAC contractor rich?
 
  #10  
Old 10-26-08, 04:43 PM
D
Member
Join Date: Jan 2008
Posts: 49
Received 0 Votes on 0 Posts
Okay, it might work for heat, but radiant floor heat is usually set at 90F minimum temp and there is insulation directly under the piping to reflect the heat upward. I'm not sure how well a heat pump would do at maintaining a 90F +\- constant temp.

As far as A/C I see no way for it to be efficient. There is a reason there are no radiant air conditioning systems.
 
  #11  
Old 10-26-08, 05:36 PM
airman.1994's Avatar
Member
Join Date: Dec 2005
Location: VA
Posts: 5,795
Received 8 Votes on 8 Posts
Take a look at this link! I think it will shed some light for you. http://buildingscience.com/bsc/
 
  #12  
Old 10-26-08, 08:59 PM
D
Member
Thread Starter
Join Date: Jul 2008
Posts: 16
Received 0 Votes on 0 Posts
heating/cooling home with crawlspace conditioning

That's too hot for a heat pump? I could try it at 80, In fact, I'm going to have to. we have a cold front moving in and I'm going to block the foundation vents and see how it works. No choice.

There are no radiant A/C systems because they use either electric or hydroponic, not forced air. It worked OK last summer even w/o the foundation vents all blocked off.
 
  #13  
Old 10-26-08, 09:06 PM
D
Member
Thread Starter
Join Date: Jul 2008
Posts: 16
Received 0 Votes on 0 Posts
heating/cooling crawl space w/ heat pump

Actually, I've already read that document extensively Airman. Especially the part "new light on crawlspaces". Maybe you'd be surprised to hear that the issues with mold and moisture with closed crawl spaces have been proved to be largely a myth (stuidies done in Florida and elsewhere). That's why new home constructions have gone with conditioned crawlspaces more and more, especially in combination with technologies like geothermal and solar , where they've been using it for years (since I first read about it in a solar book that went out of print back in the '80's).

http://buildingscience.com/bsc/[/QUOTE]
 
  #14  
Old 10-27-08, 03:38 PM
Jarredsdad's Avatar
Member
Join Date: Oct 2002
Location: Troy, VA
Posts: 1,532
Received 0 Votes on 0 Posts
Originally Posted by djsmith9 View Post
I have a physics degree
There the problem right there.

Wish I had a dollar for each time I've run into the "I have a degree, therefore if I can think it, it must be so" mentality.

Not trying to talk down to or belittle dj, but look, you come hear with an idea. Several people in the field of expertise tell you it won't work.

But, since you have a degree, you try and explain why they are incorrect.

Originally Posted by djsmith9 View Post
What'd I do to deserve this besides have a great idea that won't make some HVAC contractor rich?
It won't make anyone rich, because it won't work. If it did work, it would be an accepted option.

Lastly, Hydronic is heating with fluid filled pipes, Hydroponic is growing plants in water with no dirt.

But, it is your house. Go ahead as you plan and do what you think will work.

Please come back and keep the naysayers informed.
 

Last edited by Jarredsdad; 10-27-08 at 04:53 PM.
  #15  
Old 10-27-08, 04:13 PM
airman.1994's Avatar
Member
Join Date: Dec 2005
Location: VA
Posts: 5,795
Received 8 Votes on 8 Posts
Originally Posted by djsmith9 View Post
Actually, I've already read that document extensively Airman. Especially the part "new light on crawlspaces". Maybe you'd be surprised to hear that the issues with mold and moisture with closed crawl spaces have been proved to be largely a myth (stuidies done in Florida and elsewhere). That's why new home constructions have gone with conditioned crawlspaces more and more, especially in combination with technologies like geothermal and solar , where they've been using it for years (since I first read about it in a solar book that went out of print back in the '80's).
I have never seen any info about closed crawl spaces being a myth!
 

Last edited by Jarredsdad; 10-27-08 at 04:53 PM.
  #16  
Old 10-27-08, 08:05 PM
D
Member
Thread Starter
Join Date: Jul 2008
Posts: 16
Received 0 Votes on 0 Posts
Yet another comment from an HVAC industry hack? Where are the other DIY'ers who I was posting this message to in the first place? I don't need a bunch of half baked fear mongering from people who obviously don't understand basic physics. Sure, you may have worked your way up to manager from crawl space duct tech, but that doesn't mean you know jack about engineering JaredsDad. The comments I've read here so far indicate a below grade level of understanding in basic thermodynamics and heat transfer. Go back to feeding your kid with the money you earned refitting little old ladies with heat pumps and and ductwork they didn't need. You're more in your element there. And I'll bet 10 to 1 you DON"T have a college degree and don't know anybody who does.
 
  #17  
Old 10-27-08, 08:45 PM
C
Member
Join Date: Jan 2007
Location: West Central Indiana
Posts: 149
Received 0 Votes on 0 Posts
I would think if you have a physics degree you could get a good enough job to earn enough not to live in such poor conditions. I don't have any degrees and I live in a decent house.

Why don't you just run electric space heaters, It wouldn't be as efficient as a heat pump but at least you would have heat that wasn't from the festering crawlspace.
Good luck.
 
  #18  
Old 10-28-08, 06:10 AM
B
Member
Join Date: Aug 2007
Location: Northwest Arkansas
Posts: 20
Received 0 Votes on 0 Posts
Originally Posted by Civicminded View Post
I would think if you have a physics degree you could get a good enough job to earn enough not to live in such poor conditions. I don't have any degrees and I live in a decent house.

Why don't you just run electric space heaters, It wouldn't be as efficient as a heat pump but at least you would have heat that wasn't from the festering crawlspace.
Good luck.
Exactly what I was thinking!

Rats and cockroaches? I believe I'd be more worried about eliminating those before I embarked on a fool hardy scheme to ruin my heat pump.

Can you imagine what the ESP will be on his set up???

I find it humorous that a self proclaimed physics expert, comes on a do-it-yourself forum, looking for input to validate his wild idea, and then blasts the knowledgeable members who tell him he's nuts.
 
  #19  
Old 10-28-08, 07:49 AM
C
Member
Join Date: Jan 2007
Location: West Central Indiana
Posts: 149
Received 0 Votes on 0 Posts
Originally Posted by Bigbooty View Post
Exactly what I was thinking!

Rats and cockroaches? I believe I'd be more worried about eliminating those before I embarked on a fool hardy scheme to ruin my heat pump.

Can you imagine what the ESP will be on his set up???

I find it humorous that a self proclaimed physics expert, comes on a do-it-yourself forum, looking for input to validate his wild idea, and then blasts the knowledgeable members who tell him he's nuts.
As one of my co-workers says, its not a crime to get roaches, rats or mice, Its a crime to do nothing about it.
 
  #20  
Old 10-28-08, 07:53 AM
D
Member
Thread Starter
Join Date: Jul 2008
Posts: 16
Received 0 Votes on 0 Posts
"Knowledgable" is a stretch "bigBotty". I haven't read any intelligent input so far, just the same old self satisfied fear mongering that I've heard from the HVAC "pro's" around here.

I live in Wilmington NC (basically a swamp) where cockroaches and rats are 100 percent embedded. You can "manage" them but you can't "eliminate" them. I'm trying to make this older home liveable for my elderly mother who bought it to live near my sister.

This house was so cold, the space heaters were ineffective. She'd turn them up full blast and still be freezing cold. After blocking up the foundation vents yesterday, it looks like the space heaters are working now though. Not having that cold wind blasting through the crawl space seems to have made the difference. She may never need to turn on the heat pump now.

I plan on putting cheese cloth in all the floor vents today to keep the cockroaches out and control that musty smell today. I think the basic problem may be soived although I still am curious about forced air radiant heat and will try some experiments (eventually) and post my results. I'm leaning more towards a solar heated assist of the crawl space heating though, not the heat pump.
 
  #21  
Old 10-28-08, 08:11 AM
airman.1994's Avatar
Member
Join Date: Dec 2005
Location: VA
Posts: 5,795
Received 8 Votes on 8 Posts
I plan on putting cheese cloth in all the floor vents today to keep the cockroaches out and control that musty smell today.

You have mold in the crawl because there is no VB and the vents have been open. Can't control the RH when moisture is coming up from the ground or coming in from open vents. Fix the crawl clean up the mold and you will have no more musty odors.
 
  #22  
Old 10-28-08, 10:34 AM
B
Member
Join Date: Aug 2007
Location: Northwest Arkansas
Posts: 20
Received 0 Votes on 0 Posts
Originally Posted by djsmith9 View Post
"Knowledgable" is a stretch "bigBotty". I haven't read any intelligent input so far, just the same old self satisfied fear mongering that I've heard from the HVAC "pro's" around here.

I live in Wilmington NC (basically a swamp) where cockroaches and rats are 100 percent embedded.
Thats BS.

Any pest, anywhere, can be eliminated and kept from returning with a little effort. You have some serious problem's with this house and the sooner you address it, the better off you will be.

And if you call constructive criticism, "fear mongering" remember YOU came here asking for it.

Rather than laud the fact that you have a degree in Physics, why not start working on your degree in "common sense".
 
  #23  
Old 10-28-08, 04:17 PM
D
Member
Thread Starter
Join Date: Jul 2008
Posts: 16
Received 0 Votes on 0 Posts
spoken like a true couch potato "big botbot". I mentioned once that I have a physics degree. The same thing I do on my resume and you've obviously built up a pile of resentment. Exactly what every high school dropout does for the rest of his life. And I came here looking for some fellow DIY'ers, not a horde of mosquito-like HVAC contractors to descend on the new "Newbie" like fresh meat. And you have added exactly 0 positive input to this discussion. Look through and see what you've said since you first barged your way in. And like I asked earlier, this is your second post in over a year, what in the world made a high school dropout couch potato like yourself think he had something to add here (which you clearly didn't)?
 
  #24  
Old 10-28-08, 07:19 PM
B
Member
Join Date: Aug 2007
Location: Northwest Arkansas
Posts: 20
Received 0 Votes on 0 Posts
Wrong again.

I happen to have a degree in Civil Engineering and am a P.E.. Also a RLS, Registered Land Surveyor.

I build things for a living. I've been doing so for 30 years. I know a little bit about construction and building systems.

My first post to you had the advice to basically abandon your idea because, in my opinion, it will not work. Period.

My post count is low, that I'll grant you, but I generally work 50-60 hours a week and have little time to visit this site as much as I'd like.

You've been extremely defensive throughout this discussion, and your juvenile attacks and language, in my opinion, speak for themselves.

Good luck in your life. I have a feeling you will need it.
 
  #25  
Old 10-28-08, 08:38 PM
C
Member
Join Date: Jan 2007
Location: West Central Indiana
Posts: 149
Received 0 Votes on 0 Posts
Originally Posted by djsmith9 View Post
spoken like a true couch potato "big botbot". I mentioned once that I have a physics degree. The same thing I do on my resume and you've obviously built up a pile of resentment. Exactly what every high school dropout does for the rest of his life. And I came here looking for some fellow DIY'ers, not a horde of mosquito-like HVAC contractors to descend on the new "Newbie" like fresh meat. And you have added exactly 0 positive input to this discussion. Look through and see what you've said since you first barged your way in. And like I asked earlier, this is your second post in over a year, what in the world made a high school dropout couch potato like yourself think he had something to add here (which you clearly didn't)?
You know, I hate to get into this again.....

There are Professionals here that have no possible financial gain from giving you advice, and you insult them and argue with them after asking their opinion and disagreeing with their opinion. Maybe you should put down the physics book and get a few self help books to try to deal with your arrogance.

I still would like to know where it all went wrong, you have a physics degree, you are obviously much smarter than most folks, and yet you (or is it your mother) live in some festering old dump. You should be able to pull down good money if you get into the right field.
Maybe you should invent a Crawlspace heating system for moldy crawls with roaches and rats and maybe you can make enough to live in a sanitary house.

I understand some people do not make much money and can't afford a even a small nice house, but they can still keep it clean. It doesn't take a Masters Degree to not be filthy.
 
  #26  
Old 10-28-08, 09:03 PM
D
Member
Thread Starter
Join Date: Jul 2008
Posts: 16
Received 0 Votes on 0 Posts
The one thing I can't figure out is, some of you guys are defending your nay-saying opinions like your lives (or is it livelihoods?) depend on it. Personally, I would have bailed early on if some arrogant little prick didn't like my 2 cents worth. That's just my 2 cents worth.

And sorry buddy, I do make decent money but not enough to buy my mother a new house. She'll be stuck with it for a while now in this economy, but I'll let her know that you disapprove of her poverty.
 

Last edited by djsmith9; 10-28-08 at 09:52 PM.
  #27  
Old 10-29-08, 06:59 AM
C
Member
Join Date: Jan 2007
Location: West Central Indiana
Posts: 149
Received 0 Votes on 0 Posts
Originally Posted by djsmith9 View Post
The one thing I can't figure out is, some of you guys are defending your nay-saying opinions like your lives (or is it livelihoods?) depend on it. Personally, I would have bailed early on if some arrogant little prick didn't like my 2 cents worth. That's just my 2 cents worth.

And sorry buddy, I do make decent money but not enough to buy my mother a new house. She'll be stuck with it for a while now in this economy, but I'll let her know that you disapprove of her poverty.
Well maybe you should talk your mom into moving into an apartment. In our area there is affordable senior apartments, maybe your not so lucky in your area but I would look into it.
 
  #28  
Old 10-29-08, 07:48 AM
airman.1994's Avatar
Member
Join Date: Dec 2005
Location: VA
Posts: 5,795
Received 8 Votes on 8 Posts
Ok guys we have gotten a little side tracked here. He has come here looking for advice and we should give him a professional opinion. If are opinions are frowned upon at least we tried. (I sound like a moderator.)
 

Last edited by airman.1994; 10-29-08 at 07:51 AM. Reason: added info
  #29  
Old 10-29-08, 11:09 AM
D
Member
Thread Starter
Join Date: Jul 2008
Posts: 16
Received 0 Votes on 0 Posts
yea, I think the house is a dump but the location is great. She loves the house and is from England (where all houses are dumps apparently), so... I'm stuck with trying to make it work for her. The apartments around here are awful for the money anyways. She's better off in the house.. but thanks for the concern anyways.
 
Closed Thread
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


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