Insulating floor over crawlspace

[Cdshakes]

This must be location dependent.  Here, you either insulated between the joists, or you insulate the foundation perimeter and line the floor with plastic, but you don't do both.  My county at least prefers that the foundation perimeter is lined rather than insulation in the crawl space.  Also, cold floors IMO the insulation won't do much.  Heat rises.  You're not losing a ton of heat through the floor.  A much more effective solution is to figure out how to heat your floors.  I've no idea what kind of flooring you have and if there are any products that could go in the crawlspace between joists.  In-floor heat is usually done on top of the subfloor and under the flooring.

Good points on the heat rising.  There's 4 main rooms (living room, 2 bedrooms, kitchen... plus the bathroom).  The bathroom is ceramic tile and the kitchen is several layers of vinyl flooring.  The other 3 rooms and hallway are red oak flooring.  This house was built before they used osb/plywood as the flooring, so it's essentially 1x4's, then the oak flooring.  Since it's a vented crawlspace, my thought was there is air creeping between the cracks of the boards.  I feel like the 2 bedrooms were warmer when they had carpet and padding down.  (of course they look a LOT nicer now!)


Coliin

[Tub Brown]

Good points on the heat rising. 
Since it's a vented crawlspace, my thought was there is air creeping between the cracks of the boards. 
I feel like the 2 bedrooms were warmer when they had carpet and padding down.  (of course they look a LOT nicer now!)

Be careful on the "heat rising" interpretation.

Heat goes to cold, any direction. 
Warm air rises because it is less dense.
Heat loss is proportional to the temperature difference - assuming constant insulation.  So yes, you can and do lose heat through the floor.


If you think there is air creeping between the boards, I'd address that first. 
Can you test for that?  I've seen the $$ services that do this on This Old House.
Or from the crawlspace, blow cigar smoke at the floor and see what you smell in the house?  


From reading the advertisement regarding insulated walls/sealing your crawlspace, the benefit is a warmer crawlspace.   Of course, you're heating the crawlspace (indirectly.)

I like the previously mentioned foam option, since it'll both stop air infiltration and insulate.   The Ad mentions the negatives of foam -- IMO only the cost negative is an issue.

In our house we have insulated joists over our crawlspace which I believe was code when it was built in '88, Oakland CA.  We put area rugs in front of seating so our feet avoid the hardwood directly.

[toolmiser]

Have you contacted your "Energy Provider" with your project. Many times they have suggestions of companies that will do an energy audit with rebates thru energy provider. They will then be able to suggest the best possible solutions based on what they find. You may have other heat losses that is causing it to flow thru the floor.

I thought we had a pretty "tight" house until we got an audit using a blower door and infrared camera. I think it was money well spent and they helped pay for the "fixes". We had one done about 15 years earlier and none of the recent Leaks were uncovered.

[frule]

This must be location dependent.  Here, you either insulated between the joists, or you insulate the foundation perimeter and line the floor with plastic, but you don't do both.  My county at least prefers that the foundation perimeter is lined rather than insulation in the crawl space.  Also, cold floors IMO the insulation won't do much.  Heat rises.  You're not losing a ton of heat through the floor.  A much more effective solution is to figure out how to heat your floors.  I've no idea what kind of flooring you have and if there are any products that could go in the crawlspace between joists.  In-floor heat is usually done on top of the subfloor and under the flooring.

Good points!
The Oak Ridge National Laboratory did a study. It convinced me to encapsulate and add a good dehumidifier (Sante Fe or Aprilaire). 

https://info.ornl.gov/sites/publications...b33059.pdf


Some advantages of encapsulation:
-All penetrations in the floor were sealed with foam (cans). This should be done with either method.
-Zero mold issues as the relative humidity is now at 45%. ZERO MOLD is huge!
-All exterior vents are sealed permanently. 
-The crawl space temperature was never below 62 degrees after encapsulation.
-I used 1" foam board on the walls. In a cooler climate, use 2". 
-Leaves a 2" space above the foam board for easy termite inspection AND termites hate dry areas.
-Crawl space now smells great.
-I can safely store items there with no rusting.
-The floor was as warm or warmer than before.
-I'd use 10-12 mil plastic sheeting on the floor instead of standard 6 mil.
-Air quality is vastly improved in the living areas.

[crokett™]

Good points!
The Oak Ridge National Laboratory did a study. It convinced me to encapsulate and add a good dehumidifier (Sante Fe or Aprilaire). 

https://info.ornl.gov/sites/publications...b33059.pdf


Some advantages of encapsulation:
-All penetrations in the floor were sealed with foam (cans). This should be done with either method.
-Zero mold issues as the relative humidity is now at 45%. ZERO MOLD is huge!
-All exterior vents are sealed permanently. 
-The crawl space temperature was never below 62 degrees after encapsulation.
-I used 1" foam board on the walls. In a cooler climate, use 2". 
-Leaves a 2" space above the foam board for easy termite inspection AND termites hate dry areas.
-Crawl space now smells great.
-I can safely store items there with no rusting.
-The floor was as warm or warmer than before.
-I'd use 10-12 mil plastic sheeting on the floor instead of standard 6 mil.
-Air quality is vastly improved in the living areas.

My crawlspace is both lined and conditioned.  We use it as storage space for bulky things and/or stuff we don't use much.  It's a great place to store paint for a few years before you realize your wife changed the colors again and you're never going to use it so you throw it away....

[rwe2156]

Call an insulation company.

The difference in cost in letting them do it might not be worth the savings.

At least we found that out when we had our addition insulated the cost was only about 20% of what my material cost would be.

[blackhat]

A room temperature hard surface floor will still feel cold on bare feet. Insulating anything except the feet will not change that. Insulating and draft sealing is a good thing to do for energy consumption and comfort but it won’t change the above.

[Robert Adams]

A room temperature hard surface floor will still feel cold on bare feet. Insulating anything except the feet will not change that. Insulating and draft sealing is a good thing to do for energy consumption and comfort but it won’t change the above.

                   Encapsulating the crawlspace also does allot to improve the interior air quality.

[Cdshakes]

i've seen several mentions of air quality-- other than smell, how do you know the air quality is better?

i have a concrete floor, not dirt... doesn't really smell down there (other than being like an unfinished basement type smell)
my plenum of the hvac is not insulated, so it's already warm down there-- don't need to wear a jacket, even in the dead of winter-- was thinking about trying to insulate that a little better.

Colin

[WoodworkerTom]

I had baseboard radient heat in my last house and after the final register the return pipe to the boiler went a header with pex tubing that was stapled to the underside of the subflooring. Reflective radiant I sulation was stapled to the bottom of the joists.

Floor was about 78 degrees in the winter.

If you only have forced air I would try to heat the crawlspace and insulate the foundation walls so over time the heat raises the floor temp a few degrees. Or cheaper alternative is get and wear house slippers or indoor shoes.