Cache

I'm designing a 3-story colonial (2-story with full basement). 1200sf on each floor (basement, main, and second story). I live in a desert climate with below zero winters and 100* summers. Humidity is generally very low. Because the frost line is so deep, basements are the norm and are pretty much considered normal living space.

It seems that the preferred HVAC setup is to run the basement and main floor on one HVAC system and the top floor on a seperate system. I was hoping someone here could tell me why that is the preferred setup.

I would think that a better setup would be radiant floors in the basement with no AC unit serving that area. The hottest it ever gets down there without a furnace is about 65*.

Similarly, the top floor doesn't need much heating during the winter as the lower two floors are supplying heat if there is good circulation. Conversely, the top floor needs a ton of cooling when it hits 100* outside. So I would put the top floor on its own AC u.nit.

I guess what I'm asking is why you wouldn't rather do the following:

Radiant floors with no AC in basement.
Single furnace supplies main and top floor heat.
2 AC units, one for the main and one for the top floor.

Dustball

Money

AcDocCM

Has there been a load calc done on the home? I don't know the construction of the home therefore its hard to tell its heat loss & gains. You should ask your contractor if he has performed a load calc on the home, its the only way to know the correct size system for the home if he dosen't he's guessing!

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KesslerDweller

We build a lot of three story townhomes here in Dallas where 100+ summers are not uncommon. I would never, never have a shared unit between the top floor and main floor. The thermal gain is too much between the two. We have installed a shared system before between the 2nd and 3rd floor and the electricity bills are through the roof.

How about a dedicated unit for your 2nd floor and a shared unit between the basement and 1st floor? If you have the money, use a damper system (between the basement and 1st floor unit) so the basement can have a dedicated thermostat.

playsinmud

How well do the damper systems work/ I am currently working on a couple of 2 storeys and one three storey. And I am thinking that may be a good way to go to get proper zoning and comfort level. What do you think? Sorry I'm from manitoba canada so it's a little different then your hot summers.

Cache

That's what we are doing, dedicated unit for the top floor and a shared unit for the main and basement. Damper sounds like a decent idea if it works well and the cost doesn't overwhelm the benefits.