Design Temps

Matt_21

has weather charts for the entire country. i think this is what the majority of load programs use. the website is www.ashrae.org. you will have to buy the weather data. if you have a particular city or state i could look in the load program i have to see what the temps are.

Bob W._3

Design Temps

Is there a place online where one can find design temperatures for U.S. Cities? I have looked at the NOAA/NCDC site and other sites listed on Google. No luck so far. It looks like the winter design temp should be that temp that is colder than approx. 98% of the winter low temps, or something like that.

Also, when calculating heat loss, is there any provision made for wind? Does wind have any effect on heat loss, or would that depend on the air tightness of the heated space? Can wind increase/decrease depressurization?

A.J._2

Weather data

Some ofthe better heatloss programs like Wrightsoft have weather data and design temp. built into the program (manual J based), Just FYI.

JimGPE_17

Wind

Wind does indeed play a factor in heat loss. Most calculations assume a 15 MPH wind in the winter. If yours is more or less, I'm not entirely sure how you would correct the data.

You could get some FEEL for how wind affects heat loss by looking at wind chill tables, but they are based on heat loss from humans that tend to be trying to maintain a higher temperature than buildings, so it will only be a feel.

If you care about the reason, airflow (wind) chips away at the boundary layer of stagnant air that surrounds things, decreasing the insulating value of the barrier between the hot and cold places.

Wind also affects infiltration and will affect the pressurization of the structure. Stiff winds will increase the infiltration on the windward side, increasing the heat loss from that side.

Wind also shifts the "neutral plane" of the building, the point at which there is no infiltration due to stack effect, up higher in the building. This means that more floors of a highrise building will experience infiltration.

Bob W._3

Great info. Suspected that was the case. Thanks.

BTW, live in North Mankato, south central Minnesota. Maximum lows that I have seen, in three separate winters, has been in the -32F range with a stiff wind, enough to get -100 windchills. Hasn't been that cold since 1992-93 winter.

Bob W._3

Thanks, Matt. Mankato, Minnesota.

Matt_21

the only data

i found on my load program was:
st. paul
dry bulb summer 89
dry bulb winter -12

duluth
dry bulb summer 82
dry bulb winter -16

if your somewhere close to these you can use the same weather data.

johnnyd

design day

I don't know exactly where the info came from, but my consultant used -10*F as a design day for SE Minnesota, Spring Valley area...just about the same latitude as Mankato.

steve b_5

I do a lot of research on the Internet. Whenever I have a question I go to Google. I found the following link by "Googling" : mankato "design temperature":

http://www.revisor.leg.state.mn.us/arule/7670/0400.html

According to the State of Minnesota Rule #7670.0400 the exterior design temperature for Mankato is -17°F.

Bob W._3

Hey thanks. I googled "design temperature" but didn't think to connect it to the town.