Q–I have a big 37-by-11-foot three-season porch that is unheated. What is the best way to heat and insulate it?
The porch is set on footers and has about a 3-foot crawl space underneath. How should I insulate under the porch? I don’t know if I should try and dig below ground to place a foam insulation along and below the siding.
Also, the windows are old and will need to be replaced.
The rest of the house is hot water radiator heat and I can tap off of that boiler to put in baseboard radiators, if advised.
mattjcrawf@aol.com
A–From the information you’ve supplied, it’s going to take several steps to get your porch not only warm but also energy-efficient. We’ll list those steps, thanks to the help of John Marley, an administrator with the Energy Wise Homes program run by the Illinois Department of Commerce and Community Affairs.
Three-season porches or rooms are wonderful additions to a house. But because of the amount of glass and the lack of a foundation, they’re often susceptible to cold air infiltration.
Hence, you should address the windows first, says Marley. “No matter how much you insulate and heat the porch, it will feel cold if the windows are in bad shape.”
You simply said that the windows are old and need to be replaced. Depending on the number of windows you have (and we’re assuming it’s a lot because it’s a porch), that could be a fairly costly endeavor, especially if you move up to dual-pane insulated-glass windows.
If you can’t afford to upgrade the windows now, you should at least seal them off before adding a heat source and insulation to the porch.
Some simple steps would be to caulk the windows or install storm windows if you have them. Also, take a look at the various window-sealing kits that are available. These kits usually consist of a sheet of thin plastic that you adhere to the window and secure with a hair dryer. While unsightly, they do do the job.
Next, you should address heating the space. Marley agreed that the most efficient system would tie into your existing hot water radiator system. However, have a heating contractor inspect the system to make sure it has the extra capacity to accommodate the added space.
If you install baseboard heaters, try to place them on the exterior walls below windows, says Marley. That’s where they’ll do the most good at negating cold air infiltration. Also, try to run the supply pipes to those heaters up in the floor joists of the porch.
Also, install valves on the heaters so that you can turn them down or off when you’re not in the room.
Finally, you’ll need to insulate the porch. Marley advises using a sprayed-on icynene foam insulation on the underside of the porch floor. “By spraying the icynene on the underside of the porch, it will form an air barrier that will keep cold air from coming up through the floor,” he says.
He recommended avoiding fiberglass insulation, which could get wet in the crawl space, lose its insulation value, and then fall from the floor joists. When spraying in the insulation, place a coating of it on the supply pipes for the baseboard heaters. That will keep them warmer and help keep them from freezing in the dead of winter.
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