Thread: cheaper HVAC in attic

Recently inspected a large "high end" $1.4 million, 10 year old home. MLS and realtors described builder as "quality local builder". In many respects it was a very nice home.

However, among other things, it had non-freeze proof hose bibbs. "Quality"?

One thing I'm curious about: it has two HVAC systems. The one in the basement is a 90+% condensing furnace. The one in the attic is non-condensing. It vents through the roof with B-vent. Another example of cheaping-out, or is there a good reason other than saving $$ that they wouldn't put a 90+ in the attic also?

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Originally Posted by John Arnold

or is there a good reason other than saving $$ that they wouldn't put a 90+ in the attic also?

Not being in an area where it freezes like it does up there ... but would there be a concern with the condensate freezing with a condenser furnace in the attic?

Jerry - Good point.

Around here in upper Indiana, when a condensate furnace is installed in the attic, they actually make a small heated and cooled room with insulated walls, ceiling and a floor with a drain.

When I lived in Kentucky where in many cases they installed the condensate furnace in an unconditioned area, there were times when a heat tape needed to be installed on the drain line. I never liked this type of installation.

In my area it's common to see condensing furnaces installed in the attic, when appropriate I note the possibility of freezing condensate lines. I've followed up with clients in cases where I thought the risk was particularly severe, but so far no one has actually reported freezing problems or damaged condensate plumbing.

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FWIW, I would recommend avoiding the term "freeze-proof", I tell my clients there's no such thing as a "freeze proof" hose bib; if you look at the manufacturers actual marketing materials and installation instructions they are listed as "freeze-resistant", and they are "freeze-resistant" only to the extent that they are properly installed and operated

In my area bibs are frequently installed with a upwards pitch toward the exterior which retains water after the valve is closed, and/or they are installed in such a manner that cold air can penetrate back behind the valve at the interior and of the bib and rupture the copper waterline supplying it. And of course if you leave a water filled hose connected to any bib, that pretty much guarantees a water filled bib which can be fractured by a hard freeze. So in my opinion, in my climate best practice is to provide a readily accessible shutoff valve controlling a properly pitched supply line and bib, irrespective of whether it is intended by the manufacturer to be "freeze resistant" or not.

Another reason for the higher quality furnace in the lower level only may be a combination of physics and economics. We all know that warm air rises. If the plan is fairly open, the builder or HVAC contractor (or the owner, if it was a custom home) may have chosen to install the higher efficiency unit downstairs knowing that a lot of its output would end up on the upper level anyway. In a 2 story with areas that are open from one floor to the other, there is a lot of air transfer when one system is running and the other one isn't -- which is a lot of the time. I know that in my own home, if I sit on the stairs to put my shoes on in the summer when the 2nd story a/c is running, I can feel cold air moving down as the warmer air rises to the upper floor via a 2 story entry. I'm sure the opposite effect occurs in the winter.

Realizing that the lower level furnace would run more than the upper one, the decision may have been made to install a high efficiency one there only.

After all, the savings could be spent on a built in wine cooler or other "necessity."

I have provided 90+ furnaces in attics before with heaters on the traps but I would never do it again. IMO it is short sighted, it does not look out for the good of the project in the long term.

The ideal solution would be to install the unit in a conditioned space.