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Posted by on January 23, 2007, 8:34 pm
> I have a new house being built, and of course am running into brick
>walls with the HVAC contractor. He is more accustomed to commercial
>and industrial buildings where all the thinking and engineering has
>been done for him, so all he has to do is install.
>What I want is hydronic heat, under the floor, stapled up between floor
>joists (over an unfinished basement that also has foam insulation on
>the outside of the exterior walls). I plan on using foam board with
>foil on one side, cut to fit loosely enough to be easily installed
>and/or removed from the engineered joists.
>That will be the base load, but as we all know, changing the
>temperature of a hydronic system takes hours. So, since we have to
>pre-wire, pre-plumb, etc. for a forced air system anyway for air
>conditioning (not my idea, but making sure that the house can be sold
>someday without major mods), I want a hot water coil in the air handler
>to boost the air temperature in those occasional events when the
>domestic supervisor is cold and wants heat right NOW. She tends to run
>thermostats either all the way up or down, thinking she will reach her
>comfort zone faster that way. Really irritating in the car, I can tell
>you!
>That is the heating side of it, from my viewpoint. He says a simple
>gas furnace is the way to go, because that is pretty much what he does
>in houses. A compromise would be a modern gas furnace with 2 levels
>of heating, and 2 fan speeds that won't have to run very often based on
>the hydronic doing most of the work.
>HVAC guy also wants me to put in 4 to 5 tons of AC for a house in
>Logan, Utah. I only have 4 tons for our house in Phoenix, Arizona, and
>it gets a bit hot there. The Utah house is smaller by 150 sq. ft. but
>also has a 900 sq. ft. loft and bonus room area upstairs that is pretty
>much open to the main floor. We won't be going up there much, though.
>I warned him about oversizing, letting him know that I could live with
>a system that runs too often or too long than one that short cycles. I
>can always add to the hydronic if I have to.
>I won't put in the outside portion of the AC for at least the first
>year, thinking that I have designed the house well enough to need very
>little cooling assistance, and if it does, I prefer either a whole
>house fan, or evaporative cooling.
>Does this sound like sound, and sane, thinking on my part?
your first order of business is finding yourself a new hvac
contractor, or convince the one you have that he has to do a complete
energy load calc for both heating and cooling. Without a load calc,
all you are doing is guessing.
Next you need to find a guy who installs hydronic heating for a living
and has a clue or two about what he's doing. The hvac guy you got is
not going to cut the mustard.
You would be money ahead of the game if you bought Steve Scott a round
trip airplane ticket and flew him out to do the load calc and design
of your system. Then maybe your hvac guy would have a few clues to go
on.
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