4 posts / 0 new
Last post
Heating a Porch

Fellow Experts,

I had a screen-porch built off my kitchen. It follows the model of the "screen-door" porches that TOH ran this spring. The walls of the porch are wooden screen doors fixed into place, and we have glass storm windows to replace the screens. The floor is wood, and has 1/8 inch gaps between boards. Underneath the room is a four-foot high crawl space, built of plywood, housewrapped, and covered with fibercement siding. I could insulate the crawl space.

We like the porch so much that we want to use it all year round, but we live in Chicago, and the uninsulated nature of the room is going to make heating it a job. We would only need to heat the porch for about three or four hours a day.

My idea is to install a big electric or gas heater in the crawl space and to let the hot air rise between the floor boards to heat the room. Is this a reasonable plan?

Tom Madden

Re: Heating a Porch


I think the electric and gas heaters would present a fire hazard issue, as well as CO2 and CO issues with especially the gas heater, not to mention building codes & high expense.

The safest, and most economical way, would be to tie the porch crawl space in with your current heating system, preferably by a zoned setup.

That way the flame products would not be an issue, and you would save a lot of $$$.

What type of heat do you have in the main house???

Re: Heating a Porch

To Jack the Shack et al

We have hot water heat. The heating guy who cleans our boiler says it would cost about 3000 to run heat from or boiler. This is not what I want to hear!

Re: Heating a Porch


Don't give up. There are a lot of different ways to heat an enclosed porch.

It's a matter of finding the right contractor.

If you get 5 or 6 more estimates you will get that same number of different ways to skin this cat.

That quote of $3k is way high.

I can rattle off several options:

1) Since you would have a freeze problem with a forced hot water extension from your present system, it would mean adding antifreeze to the system (not recommended because it affects some of the system's components), or going thru a heat exchanger w/the propylene glycol, such as a zone-valved Amtrol indirect HWH, then pumped baseboard with a t-stat; this would probably cost a lot.

2) a small direct vent forced hot air oil-fired or gas-fired furnace of ~40k btu/hr would cost $500 plus installation; with something like this you wouldn't have to worry about anything freezing; the forced hot air would be there if & when you wanted to use the porch; it would do a fast job of heating up the space.

3) A large AC that both heats and cools is a possibility.

4) Electric baseboard, although you would need probably 40 amps available on your main panel & at 14 cents/kwh, would cost you $2-$3/hr to use.

You should also do a HEAT LOSS CALCULATION of the porch so you have an idea of what size heating unit you will need.

Take the square footage of the porch & multiply by 50 to get a crude estimate.

The site below will be a little more accurate.

Consult the Yellow Pages under "Heating Contractors"; and get several more estimates.

I think you'll eventually find the right contractor at a reasonable price.

For further info, Google "oil-fired direct-vent heater/furnace", "gas-fired direct-vent heater/furnace" (with & without the quotes).


Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.