Air Change Per Hour Question

GW

I just bought his CD, haven't looked at it yet. It was so cheap I coundn't resist.

Gary

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GW

Air Change Per Hour Question

Hello Wall,

I'm trying to tighten up on some up-front clauses. Can anyone tell what what kind of Air Change Per Hour I may want to jot down in my "small print"? I'm more than happy to gaurentee my work, but if I get called on it, I want to be able to CONFIRM that house is at least average in air changes.

My Elite program is saying "average" is .75 for heating season, and .35 for cooling season. This is for a 1500 sq ft house. Are these numbers good to go? Thanks for any input.

Gary

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Mike T., Swampeast MO

Up-Front Clauses

Be careful. I SERIOUSLY doubt that you can oversee and control the construction of a structure--it's really not your job anyway...

Unless you can actually [confirm] infiltration at a given time and given set of circumstance via a very well controlled pressurization (blower door) test, you really have no idea of the actual infiltration.

You can only use "generally regarded as safe" calculations....

GW

my thoughts exactly

That's why I don't want to hold the bag if the building sucks (or has too much air change...)

How on God's green earth can a contractor gaurentee his fine work if he has NO IDEA what's in the walls? Or what's not? It cracks me up about people in the trade tooting "where's your heat loss/heat gain, kiddo?" It's a big joke, imho. Don't the programs need air change entered?

Gary

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[Deleted User]

hi Gary

this info is from siggy's new book, which he has at his web site www.hydronicpros.com-----he breaks it down into three catagories, best,average, and poor construction..and also by the sq.footage of the room/house..
for best construction <900 sq.ft. 0.4 , 900-1500 sq.ft. .04
1500-2100 sq.ft. 0.3 , over 2100 0.3
for average construction <900 sq.ft. 1.2 900-1500 sq.ft. 1.0 , 1500-2100 sq.ft. 0.8 , over 2100 sq.ft 0.7
for poor construction he has <900 sq.ft. 2.2 , 900-1500 sq.ft 1.6 , 1500-2100 sq.ft.1.2 and over 2100 sq.ft. 1.0
also for fire places he has to add for best- .1 average .2 and poor .6 to the air changes...kind of hard to duplicate his chart in narrative form, but i hope this info helps out.

Al D'Ambola

Air Changes

Gary,

ASHRAE standard 69-82 states a home should have .35 air cahnges per hour which is 8.4 per day. The only way to measure this is with a blower door.

I woild think our first responsibility as HVAC Professionals is to verify that our systems are doing there job, before I deal with the envelope.

Measure CFM, multiply by your system delta-t(measure temp at supply grilles & returns)X 1.08 = BTU'S. Once you have proved that your system is working correctly, then do a blower door test and see how the envelope is performing.

Do you measure the air changes per hour that the mechanical system is delivering?

S Davis

HRV

I think as professionals in the heating industry we should be thinking about fresh air requirements, and advising our costomers about the need for fresh air in hydronic systems.
We sell and install Heat Recovery Ventilators and include air filteration.
Keeping fresh air requirements in mind as we do our installs also helps avoid draft and vent problems.
Just my thoughts.

S Davis