heating degree days

[Deleted User]

Thank you guys,..both have been very helpful!

Hollis

Heating Degree days?

Anyone in the oil heating business? I keep hearing that they use heating degree days as a tool for deliveries. A few people that I have asked (mainly people working in the front office of oil companies and perhaps not really knowledgeable of this) say that its very accurate. However in my house it seems in the dynamics of heating (we get aprox 6,000 HDDs) My impression is that I use a lot more oil during the mid 2,000 than the first or last 2,000. Do you find this is true with other houses or is my house have problems? (I THINK its well insulated and weather stripped)

Also it seems to me that HDD don't take in to account of high winds or a lot of sun or cloudy.
I would think that oil companies might use something like a certain sized and certain gauge aluminum box painted flat black with a small heater (bulb?) with a good thermostat to keep it say 70 degrees inside in an areas that gets max sun and representative wind and a good electric meter. After developing a formula for electric use and oil use wouldn't that be closer to a tool for measuring how much fuel you will use? Or is the averaging of HDD so telling that its all that is needed?
Is my house not typical?

Brad White_203

Heating Degree Days

Hi Dwayne, Heating Degree Days or HDD (Not to be confused with "The Other HDD" or HeatingHelp Delirium Disorder), is accurate to the extent that you use it correctly.

As with any "one size fits all" formula, it underscores that your home is unique. For example, the sun may strike more fully and directly on vertical glass in winter (as it does in the northern hemisphere) and your shading from winds is unique too. You may have deep evergreen hedges to the north and west, or a barren plain resembling Alberta.

I assume you know the formula, (heat loss x degree-days x 24 hours) divided by (Design indoor-outdoor delta-T x system efficiency x BTUs per Fuel Unit).

This will give you a raw, gross number of units of fuel used, either therms of gas or gallons of oil, gallons of propane, whatever you use.

The next step is the "Cd" factor. This can be, in a 5500-6500 degree-day area, anywhere between 0.50 and 0.65 and is, as far as anyone can tell me, entirely empirical. (Empirical means "we made it up but it squares with experience".



For my area, Boston, we get an average of 5,641, I use a 0.60 factor which of course reduces the actual gross number to closer to a net number.

Now, this Cd factor absorbs or accounts for things like internal gains, use of night set-back, solar gains, thermal storage in the structure, variations in infiltration, everything that has some bearing but is also "miscellaneous".

Not sure this answers your question, but it might get you thinking differently to where there might be an "Aha!" moment.

John@Reliable_14

Degree days.........

is only one part of it.Degree days along with the "K" factor will give you a almost fool proof system. Degree days and fuel usage between two (more is better) delivery's will give you the magic k factor.This takes into the fact that no two households are the same.

Dick Charland

Beware however of the useable tank figure, the DD system works well given some history on the account, unfortunately management in trying to stretch deliveries will set useable gallons in tank from 180 to 200 or higher and it doesn't take much to have a bunch or runouts. All the information should be on the ticket, deliveries, gallons, dd's, K factor, tank size and useable.

[Deleted User]

So can one establish a formula to how YOUR house is doing compared to averages by applying a HHD number to a K factor? (not sure what is a DD,..a delivery date?