What's the official method of heat lossing a room?

Constantin

... go to the <a href="http://www.acca.org/tech/manualj/">ACCA web-site and buy Manual-J</a>, or a Manual-J based software solution. Tim likes to do his heat loss calculations by hand, perhaps he can help you further in finding good paper and pencil based resources.

Keith_11

What's the official method for heat lossing a room?

I've used slant/fin's program, but I'd like to know the pencil and paper method. . .none of my literature seems to mention it.

Thanks

Steve D._3

The software you used is based on I=B=R H-22 book. You can do it pencil and paper but it is time consuming. You will use values for heat transmission which presumably the software looks up for you. You are probably trying to get a feel for what is in the calculation but the book won't really tell where the factors are derived. You will get a check if there is something amiss in the program or your entry.

I made a spreadsheet for this but it is tailored to the number of rooms in my house. If you are good with excel and lookup tables I could send it to you.
Good luck
Steve

Tim_24

The simplest P&P method

is defined by the equation UAdT=h, where:
U =1/R which is determined by the construction details,
A = the area of the exterior surface(s),
dT = the inside desired temp (70 degF) - the outside design temperature (depends on your location) and
h = the heat loss in btu/hr.

Use this equation for ceiling, walls, doors & windows and for air infiltration/exfiltration.

Rooms with 0 exposed walls, can be assumed to have 1/4 air change per hour (ACH), this is based on 2x4, 16" o.c. R-11, semi sheathed (corner bracing only) and some type of lapped siding), 1 exposed wall, 1/2 ACH and with 3 exposed wall, 1 ACH. For houses with better construction than described, lesser values apply. To calculate the heat loss due infiltration, (room volume x ach x 1.085 x dT)/60.

Add all the various parts up, add 10% to each room with north and/or west exposures. For ground level spaces, on aslab or over an unheated basement, heat loss for the first 3 feet of the foundation wall must be added to the other elements of a room heat load.

Determining the R values of elements and design conditions are the most subjective parts of the process.

I have an old memeographed form that was developed in the 40's or 50's, that basically summarizes the elements described above. The same method is described in the latest (2005) version of the ASHRAE Fundamentals Handbook. Also referenced in this handbook are the ACCA's Manual J, as previously mentioned, and other methodologies that is specific to heat GAIN determinations, which are significantly more complicated.

Big Ed

Hit the Books

I use paper and pencil and use the work sheet in the book " Modern Refrigeration and Air Conditioning".. page 1048 .