central air on residential flat roof 1

[CivilizedPE]

What are the options for constructing a central heating and cooling system in a house with a flat roof, no attic and slab on grade foundation? The home is 1400 sq ft with cinder block exterior walls and currently has an evaporative cooler on the roof and gas wall heaters. All ideas are welcome.

 

[MintJulep]

Conventional ducts above the roof. Diffusers and returns in the ceiling. Hope the penetrations don't leak too much.

High-velocity system, distribution could be tucked into soffits, at least in part. Hope the penetrations don't leak too much.

 

[chicopee]

If possible about attaching a mechanical room to the house and have wall penetrations for ducting.

 

[CivilizedPE]

What are everyone's thoughts on raising the roof, pitching it and then running the duct work?

 

[MikeHalloran]

If I was going to raise the roof, I'd strongly consider adding a second floor while doing so.

At home in SoFla, it's not uncommon to see an entire system mounted on a flat roof, external ducts and all, insulated and painted. Clearly somebody sells horizontal weatherproof air handlers for that servce. I have no idea how they seal or flash the penetrations; I'm guessing lots of hot tar.








Mike Halloran
Pembroke Pines, FL, USA

 

[IRstuff]

I've certainly seen A/C units on the roofs of residential buildings, but hanging the system on the roof to set in the hot sun seems like a serious efficiency killer.

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[MikeHalloran]

I think UF has done research indicating that providing shade, specifically nearby evergreen trees, for the condensing unit, still typically aside the house, does improve efficiency.

A rooftop evaporator exposed to the atmosphere atop a flat roof is probably operating in a more benign environment, efficiency-wise, than the same evaporator installed under a moderately pitched roof. ... and is easier to access for service.




Mike Halloran
Pembroke Pines, FL, USA

 

[chicopee]

One of our clients installed a wood frame canopy with corrugated translucent fiberglass panels over their skylight in one of their fast food restaurants; the same type of sun shade could be useful for roof mounted Heat/AC unit.

 

[msquared48]

I have never run into a roof mounted residential or commercial A/C system where the noise from the air handling units was not irritating to someone. This would be particularly noticeable in a 1400 square foot house. A ground mounted system would be much better in my opinion, and, if the space is available, could be located on the north side of the house in the shade. If you have to, use open web trusses in the roof structure to run the ducts.

Mike McCann
MMC Engineering

 

[boo1]

Consider mini split wall hung units. Roof penetrations will haunt you.

 

[jistre]

Mini-split. No ductwork and no roof penetrations.