Age old question?

Dave_4

between the inside and outside is what drives heat loss, as noted.

Up here in Presque Isle, ME it was a balmy -10F this morning outside my 100 year old oil-fired steam-heated house. At 60F indoors that's a 70 degree difference inside to outside (delta-T). At 70F the delta-T is 80 degrees, obviously.

I'm not sure how to factor in boiler efficiency, run time, etc. but on the delta-T alone the warmer temp costs at least (80/70) times as much, which is 14% more. Just adding to the pain at $3+ a gallon!

Now assume it's 35F outside, so delta-T is 25 and 35 degrees respectively (for 60 and 70 inside temps). Your heating bill for that mild winter temp will overall be much less compared to -10F outside, due to the absolute difference being smaller.

However, the *percentage* penalty for keeping your house at 70F instead of 60F inside will be proportionately larger since 35/25 = 40%...
you'll definitely notice that in the bill!

does this sound logical?
-Charles

huck_3

Love this site and all the help you've given me.
Here's one that's puzzled me.
My dad, who worked in heating repair his whole life, and I have always disagreed on the answer.

Will I be burning (virtually) the same amount of gas to keep my house at 70 degrees vs. 60 degrees?

The house is almost 100 years old, single pipe steam radiator, boiler is only a few years old and the system is well balanced and has new Gorton vents.
My thought is that, with the heat loss in this old house The boiler will be firing a lot more often to keep it at 70 degrees, so we keep it cold around 60 degrees.

But if it's always 35 or lower outside, is the heat loss any different if the house is 70 or 60?

I'd love to hear any educated thoughts and opinions on this, and of course my wife would be overjoyed if we kept the house @ 65.
thanks,
tom

Unknown

A simple answer,

your house is basically a "box" requiring an internal temperature for your comfort. This "box" is located where the outside(ambient) temp. is (depending on the season), cooler outside.
As heat is attracted to cold, insulation around the "box" determines the rate the warmer temp will transfer through walls, floor, roof and windows to the outside.
The higher the temp diff between outside and in, the more fuel you will use to maintain that difference.

Dave

Brad White

Yes

The heat loss is proportional to the difference between indoor and outdoor temperature. It will always cost more to heat a house to a warmer temperature at a given outdoor temperature.

Where this aspect goes a little wobbly is the idea of night setback. There is a mixed bag of experience with all of the variables of building mass, insulation, integrity of that insulation (the reality versus what you think is installed) and the envelope air tightness.

Some say that any energy saved in a given night's setback is lost during a prolonged warm-up period, thus a slightly reduced but constant temperature is preferable. Others say "drop the bottom out" of the thermostat and enjoy the fact that at night there is less heat loss (less delta-T presumably) and the boiler runs less.

Too many variables to consider. My own jury is still out on a definitive answer.

But all other things being equal, a given house at one temperature versus another temperature will cost different amounts to heat.

Mike T., Swampeast MO

Huck: If you constantly maintain the house at about 60F you will use significantly less fuel over a heating season had you maintained the house at 70F.

If you daily adjust the thermostat between say 60F and 70F things get far more complicated and energy savings as related to comfort can be very difficult to achieve.

Pringles

FACT

The lower your thermostat is set the less fuel you will burn..... period.... end of story!!

Unknown

Mechanic

Whoa,,,there are many variables here we are trying to point-out!

Dave

Mark Hunt_3

Allow me to quibble


No!! Not really!! I just miss seeing that on The Wall!

Brad and others have nailed it.

Here's proof.

What would your heating bill be if you kept the house the same temp as the outdoors?

No difference = no bill. (Although the alimony payments would be KILLER!)

Merry Christmas!

Mark H

huck_2

Thank you for all of the wise input.
I now feel confident in my position that keeping the house at a fairly constant 60 is burning less fuel than keeping it at a fairly constant 70 degrees, and thus helping to keep our gas bill under $350/month.
With all this extra money saved, I can buy my wife the electric heat blanket she's been begging from Santa.

Thanks again for your responses, you guys are always right there with the answers. All the time.
Merry Christmas...
and a warmer new year.