Air Infiltration/Heat loss for open over head door

SM

I am sure I have seen a forumal for figuring heat loss for an open door based on the sizing of the opening, difference in outdoor temp to indoor and the amount of time per hour. Can any one help me with this? I have a customer that is think about radiant heat in a new garage. The 9 x 10 overhead door will be opened for aprox. 5 minutes every hour during the day. Do you have to size the system bigger for this? Or will the thermal mass of the concrete enable the room temp to recover on its own?

Thanks
Scott

Mark Eatherton1

The BTU's in the floor....

are just waiting for the chance to jump out of the slab and squash those cold, heat robbing slugs of cold air.

5 minutes per hour ain't nothing to the mass potential of a slab holding heat at 85 degrees F.

Someone may counter my opinion, but if it were me, I wouldn't worry about it. 90% of the systems that are out there are WAY oversized anyway...

ME

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Art Pittaway_2

The best formula is

to have him call one of your former customers and gets an ear full of how stupid he will be if he doesn't let you put in radiant. Had one of my customers tell a prospect that his system was "the cats pajamas". The prospect said he didn't know what the guy meant but he was so happy with it that he had to put in radiant also.
Good luck.
Art

Steve Ebels

Don't worry about it

We did a 6000 sq ft auto repair shop last year. It has a 14X16ft overhead on each end of the building, North and South. One of these doors is cycled up/down about 4-5 times an hour. The owner says that 2 minutes after the door is shut you can't tell is was ever opened. The floor can dissipate an enormous amount of heat when that cold air rolls across it. (Higher delta T)

In his previous shop he had forced air which had a terrible recovery time when the doors would open. The unit heaters would run for 15-25 minutes after everytime it was opened up. No problem at all with the radiant.

hr

It would depend also

on the mass and temperature of the equipment you are driving in. Balance that against the amount of BTUs stored in the slab.

Delta airlines built a repair hanger with radiant floors. Imagine the size of the door that allows a 747 to be driven through. The weight of a 747, I'm guessing 200,000 lb pounds??

They did some studies on the recovery times for the temperature in the space after the cold bird was parked and the massive doors closed.It has to be much better than suspended air handlers and a cold slab.

The 10,000 square foot shop I'm working on with 6" slabs took close to 200 yards of concretre. At 4000 lbs per yard that's 800,000 lbs of stored heat. "Unleash the beast" that's a lot of stored heat waiting to be released at the speed of light,(360,000 mph, I think) to a cold object.

hot rod

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Art Pittaway_2

Farm implement

dealers often use aircraft hanger doors. Had a J.D.dealer in central Il. put in a new shop. Two huge doors, contractor didn't quite finish the controls and set it"real low", on monday the shop was over 90* at 10*F outside. Next year the Case dealer put on an addition...with radiant, the whole side of the building is one huge door.
Art

JimGPE_3

Speed of light -

186,000 miles/second.