Bathroom above a crawl space
My wife is a wheelchair user and spends 3 hours in the bathroom each morning. She needs a warm bathroom. Our bathroom is an add on and is built above a 15′ x 10′ crawl space. The rest of our home has a basement. Our home has baseboard hot water heat using a boiler. To make the bathroom floor warmer, we had 3 five foot heating elements with fins added to the boiler system in the crawl space. We also installed Tempshield double bubble reflective insulation over the crawl space floor and side walls. The boiler does not run often enough this time of the year to determine if what we have done will warm the floor. So far, after 2 weeks, it has not. The crawl space is now at about 68 degrees and the bathroom is at 71 degrees. Do you think what we have done will raise the heat of the floor tile in the bathroom? Maybe,we will have to wait until October to find out when the outside temperatures increase. Thank you for your thoughts.
Answer from Green Energy Efficient Homes
I’m not sure I understand some of the particulars here – 1) is the crawl space only for the bathroom (ie. is the bathroom 15′ x 10′)? 2) if the bathroom is smaller than the crawl space did you put the extra heating elements throughout the crawl space or concentrate them under the bathroom? 3) are the heating elements on the floor of the crawlspace, against walls, or close to the ceiling? 4) is the reflective insulation the only insulation in the crawl space or was it added over top of a decent R-value insulation against the walls?
It seems to me that if the goal of heating the crawl space is to heat the bathroom floor, you want to make a few changes:
Minimize heat loss to the outside by ensuring you insulate with something more than a radiant barrier – e.g. 4-6″ of mineral wool or fiberglass along the walls to get to R-13 to R-20. Reflective insulation has a very low R value as it is quite thin, and is generally not useful unless there is an empty air space between it and the heated space; putting it directly against a wall or floor means the R value is negligeable. For 1/4 inch thick Tempshield insulation, for example, you are probably getting less than R 1.5.
Concentrate the heat source close to where you want the heat – ie. close to the ceiling of the crawl space directly under the floor of the bathroom.
If your crawl space was built properly there should be insulation between the joists in the floor below the bathroom, which is going to reduce heat transfer from the heat source to the bathroom floor. The ideal solution if you want a warm floor would have been to install radiant heating in the floor itself, but that train may have left the station. Still, improving the insulation on the ceiling will certainly help.
From your description I can’t tell if what you have now will give you the comfort you want in winter, but your doubts and experience so far suggest it may not. It sounds though like it should at least be an improvement over what you had before. You may also find that you use far less energy just placing a portable electric heater in the bathroom and turning it on in the morning (you could even have it on a timer so it goes on just before your wife wakes up) and off again later in the day. A 1500 watt heater should be able to heat a bathroom quite nicely in fairly short order.
In general I’m not in favor of heating a crawl space unless there is plumbing in the crawlspace or in the floor above it and you need to keep supply or drainage pipes from freezing. Given that crawl spaces are generally poorly insulated (especially ones where the residents experience a cold floor above it), heating a crawl space is almost like throwing heat you’ve paid for straight outdoors. It’s much more effective to insulate the crawlspace walls and ceiling and seal the floor with 6 mil polyester wrap to keep moisture out. One other option if there is room along the walls of the washroom would be to move one or more of the radiators that are currently in the crawlspace into the bathroom itself, or at least to redirect a portion of the boiler water line to a new radiator in the bathroom. With a well insulated crawlspace and a modest heat source in the bathroom your wife should be much more comfortable.