How high a percentage of glass (sq. ft.) before radiant floors become a reasonable option?
In 1998, we purchased a house in NY right on the border between climate zone 5 and 6. It was dark…. I mean, really really dark inside and out. The house was 1.5 stories and about 1500sqft with a large room in the front with a high cathedral ceiling. Limited windows, large 2-car garage taking up the southwest corner.
In 2000, we (over)react to the lack of sunlight and I put on a 500sqft addition with cathedral ceilings and remove as many interior walls as I can. Much of the west wall became french door panels (some fixed). The three operating windows of the addition were large (40+ sqft) and there was a window seat with a similar sized fixed window. There was so little available wall space for hydronic baseboard that I explored radiant heat. I go all in and remove all the baseboard in the rest of the house. I purchase a 55gal oil fired water heater for $1k and $5k for a mile of piping and a ~1000 aluminum sheets. After endless hours of knuckle-breaking labor (and hand-molding every one of those aluminum sheets) I had a system that heat our house comfortably…… but it wasn’t cheap: I burned about 700 gallons of oil a year.
In Jan of 2016 our home burned to the ground. Nobody was (physically) hurt, but the fire was intense enough to crack the foundation. I have that rare opportunity to start completely from scratch. There are some things that will be different (get that garage out of my house footprint! let my roof just be a roof and get those mechanicals out of my attic!) but some things will be the same: Our property is beautiful and we like to “bring it inside” as much as possible, so the floor plan probably has even more glass than before. The current design has an 18ft folding (or sliding) wall into the screened porch taking up nearly half the west wall. Another key difference is that the first floor ceilings have been raised to 9ft, but no more cathedral ceilings.
The thought of re-installing the radiant heat system in DIY-fashion again fills me with dread. (The heat source would be different this time at least.) There is a good chance that I will use 3/4in maple flooring again. While I won’t have to deal with two sub-floors in the new house, I seriously doubt that the under-floor screw-up aluminum tracks will be sufficient. I made a promise that I would never ever never mold another sheet of aluminum. However, when I look at the prices of warmboard I get the uncomfortable feeling that I will be a man forsworn…..
I’m satisfied with my envelope, a 12in double-wall, and I have a good plan for air-infiltration. I have not had my mechanical engineer buddy do a true manual-j calculation yet, but the freely available software I have used puts my heating load in at ~25k. Unfortunately, that 25k is a composite number and won’t really tell me how it will feel to sit in the great room next to all that glass. I’m prepared to invest a fair amount of $$ for good glass, but glass is still glass…..
Good grief, that was a long preamble…… The actual question:
Can a locally-under-performing region of an otherwise high-performing house justify the use of radiant floors?
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