Home>Discussions>INSULATION & HVAC>Heat/AC Setting: Your Opinion
12 posts / 0 new
Last post
Poison Oak
Heat/AC Setting: Your Opinion

I am sure it costs more to keep a house air conditioned at, say, 72 degrees than at 80, and it costs more to use the a/c than an attic fan on cooler days. But I've always heard different opinions about leaving the a/c off or set at a higher temp while we're at work all day and turning it on when we get home. I've been told it costs more to cool a house from 95 down to 76 than it is to leave it at 76 to begin with, because the a/c uses more energy and works harder to cool an entire house than it does to maintain a cooler temperature. We normally leave the a/c at something like 80 while we're gone and drop it a bit after we get home. In the winter we normally set the furnace at 60 if we're gone all day (and when we go to bed at night).

What say you guys?

HoustonRemodeler
Re: Heat/AC Setting: Your Opinion

Poison,

You certainly opened a can of worms for us. There is a long standing debate on this forum about how much of a temperature swing is good before the inefficiencies of re-heating / cooling starts to make a difference. A search of the past postings will reveal looooong debates.

IMHO there should be no more than a 7 degree range between your away temp and your at-home temp.

We'll see who chimes in this morning.

Sten
Re: Heat/AC Setting: Your Opinion

I agree with Houston

Poison Oak
Re: Heat/AC Setting: Your Opinion

Oops! Sorry 'bout that. Evidently my search skills aren't up to snuff. If anyone would be kind enough to provide a like to an older thread I'd be content with that.

I'd never heard of the 7 degree range, though.

Thanks for the response. We'll see if it takes off......

dj1
Re: Heat/AC Setting: Your Opinion

The 7 degree rule is an energy saver, and since we all agree that "heat" and "cold" are relative terms, most people really don't need a wider gap in temperatures to be comfortable.

CA code for places like RCFE (Residential Care Facility for the Elderly) doesn't require the temperature to be set at 78 no matter what. So if outside temp goes up to 110 in the summer, the state will accept 90 inside (20 degree difference will "feel" cool inside the home).

For those who have to have 78 degrees, keeping the A/C going regardless the cost of cooling is the only way.

For me, a relative relief from very hot is all that matters, so I keep my A/C off while I'm away, turn it on when I return home and keep my money in the bank for more important things. My wife agrees!

On the other hand, "heating" is almost a non issue around here.

Poison Oak
Re: Heat/AC Setting: Your Opinion
dj1 wrote:

The 7 degree rule is an energy saver, and since we all agree that "heat" and "cold" are relative terms, most people really don't need a wider gap in temperatures to be comfortable.

CA code for places like RCFE (Residential Care Facility for the Elderly) doesn't require the temperature to be set at 78 no matter what. So if outside temp goes up to 110 in the summer, the state will accept 90 inside (20 degree difference will "feel" cool inside the home).

For those who have to have 78 degrees, keeping the A/C going regardless the cost of cooling is the only way.

For me, a relative relief from very hot is all that matters, so I keep my A/C off while I'm away, turn it on when I return home and keep my money in the bank for more important things. My wife agrees!

On the other hand, "heating" is almost a non issue around here.

Oddly enough, sometimes I feel colder when the temp is in the 30's or 40's than I do when it's in the 20's or teens.

dj1
Re: Heat/AC Setting: Your Opinion
Poison Oak wrote:

Oddly enough, sometimes I feel colder when the temp is in the 30's or 40's than I do when it's in the 20's or teens.

It's not odd at all, cause when you hear the weather forecast, your brain is prepared to face the extreme weather or maybe you dress warmer, so you are mentally and physically more ready. That's why low 20's don't feel much worse than mid 30's.

The same with a heat wave: 120 is bad but doesn't feel much hotter than 105, when you know it's coming.

Re: Heat/AC Setting: Your Opinion

I think a lot has to do with the home and the type of HVAC system you have. You would probably save more with a set back if the home was poorly insulated than you would if it was well insulated. The length of time plays a role as well.

Systems that are more rightly sized will have longer recovery times and set backs don't make much sense in those situations. My new boiler takes a lot longer to recover from a set back than my old one. So I gave up the set back. I am still saving money vs. the older system and the house feels far warmer because the structure of the house and everything else in the room is warmer.

eline65
Re: Heat/AC Setting: Your Opinion

I'd first go for an energy audit from a reputable company (if they reccomend upgrades over a few grand then run) Just sealing the ductwork saved my 55yo house about $100/mo or so in AZ summer.

The savings all depends on the area you live, the shading your house has, and the effectiveness of the insulation your house has. If it holds it temperature pretty well, then lowering it in the evening could might not save you money. but where I live, it's well over 110 on a regular basis, and my house bakes in the AZ sun. So turning it up to 80 in the day give the A/C some relief when the brick walls and steel framed single pane casement windows start heating up in the afternoon. Later, when the sun goes down, I can turn it back down to 74 so I don't sleep in a sauna. ;)

p.s. yes I know I can upgrade my windows, but who is going to give me the +$5G's needed for that?:eek:

motoguy128
Re: Heat/AC Setting: Your Opinion
eline65 wrote:

p.s. yes I know I can upgrade my windows, but who is going to give me the +$5G's needed for that?:eek:

Plus it will take you 100 years to recover that $5k... and replacement windows will likely wear out in as early as 15-20 or could last as long as 40-50 depending on quality. Not to mention that metal casements are really nice. They will last forever if cared for properly.

For 1/4 that price you can get nearly as much improvement in insulation value with a storm window.

ed21
Re: Heat/AC Setting: Your Opinion
Poison Oak wrote:

Oddly enough, sometimes I feel colder when the temp is in the 30's or 40's than I do when it's in the 20's or teens.

If you have a heat pump that is a common question. It's because when the temp is in the 30's the air coming out of the register is fairly cool, not much above the room temp.
When it is colder, the auxiliary heat, usually electric resistance, pumps out a lot hotter air.

It's something I've noticed in my gas forced air heated house sometimes too. I think it's because he colder it is,the more the heat is running distributing the hot air. When the outside temp is warmer, the heat doesn't run as often allowing drafts and cold spots to develop in rooms. I also tend to dress warmer when the outside temps are in the 20's even in the house.

Pages

Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.