Very hot attic's effect on air handler performance?

knichols10

Our attic is extremely hot - mostly due to a metal roof over 1x6 slats. So most of the attic ceiling is the metal (no decking). Our air handler for upstairs is located there, and on these very hot days, I'll set the air upstairs to 72 degrees and monitor the bedroom vent air temperature which never blows lower than 80-82 degrees. My question is - can the extreme heat in the attic pull down the performance of the handler and cause hot air to be blown out the vents?

bobinphx

sure can. Putting the air handler and the vents in the attic, an attic that it sounds like has little to no ventilation will indeed add heat load to the system. I suggest wrapping all the ducts in the attic with added insulation (id did mine up to r32?? 2 xr13 and 1 x r8) and it really helped and lower my bill too!!!!

I would be careful about insulating the air handler, as warranty and or servicing it might get tricky.... but if done right, it shur does help.!!!!

joecaption

Your going to have to figure out a way to vent that attic also.
You may be stuck with gable vents.
Also how much insulation do you have on the ceiling, what area do you live,
has the attic ever been air sealed?

knichols10

This is a 110 year old farmhouse - and has not had any insulation ever put in the attic ceiling. There is old blown-in insulation in the floor, but my thinking was that the problem is the heat coming into the attic from the celing, and not the heat escaping from the attic. But I'm no expert and could be way off. We live in western North Carolina and it's usually not a problem - but with the weather this summer...and no, the attic is anything but airtight. I just didn't know whether an a/c company could do anything about the situation.

biggles

are you getting a true return ducted air to that air handler from the condition space and is it tight no sucking in attic air.the on the supply side are they tight not leaking air.that attic is adding load to the second floor rooms

ben's plumbing

as mentioned above ...attic itself needs vented somehow....duct work for air should be insulated and tight to leaks.....make sure return air is tight to living space and not pulling attic air into system.....

scottmcd9999

Definitely insulate the ceiling. It's nearly impossible to cool a living space with a huge block of superheated air pushing it's way into the space.

And as mentioned earlier, ventilate the attic.

I'd concentrate on those two things first, and then _maybe_ consider re-insulating the ducts. While there can be some value in doing this, in many cases it's just a waste of time, money and effort - and in many cases, it's dang near impossible to do.

joecaption

http://www.energystar.gov/index.cfm?...sulation_table

Here's some suggested minumums for insulation.

Here's just some guesses on things on things you may be dealing with that I've found on the dozens of 100 plus year old houses I've remodeled.

Ballon constrution, so the walls are open from the crawl space or basment to the attic. The walls need to be blocked at the bottom to cut off the air flow.

No one has ever air sealed all the holes where wiring and plumbing were run in the bottom plates. They need to be sealed with expanding foam.

Someone may have installed replacement windows but never removed the trim around the window to insulate the huge holes on the sides. In most cases there's about a 4 to 6" wide hole direct to the outside where the old window weights were, and about a 2" at least gap under the window and also the top.

No one has ever sealed up where the lights, ceiling fans, vent pipes, and wiring were run in the attic. A simple sealing up with some foam will fix that.

Just because the home is old and has never had any vents does not make it a good idea. Lots of old homes had no insulation at all, no soffit vents and no roof vents. But they also never had HVAC to heat and cool the home, now you do.

All of these things will not cost, they will save you money and there all simple easy DIY jobs.

FrankL

You can also get solar powered attic fans. Lowes has one for $221 - it moves 800 CFM. I was thinking solar because you would not have to run electrical up there. Non solar is about $131. Lots of people sell them on the web and Costco has some good models.

scottmcd9999

I've heard mixed reviews on the solar powered fans - they don't move enough air, they don't run if there is ANY cloud cover, they aren't very reliable, etc etc. Others love them, of course, but for the cost of running a few feet of 14/2 wire, I'd go with the 120v model.

FrankL

I think you are probably correct Scott. Sounds like a good idea but an electric version moves a lot more air and is cheaper.

This fellow might be able to get a roof fan or a gable version too.