Hi folks,
   Can you please answer this: I audited a home built in 1925, no insulation in walls or attic, 1 story, 1298 sq ft,  on raised foundation w/ lamineted floors, home recently redone, hvac leaks 30%  and blew a 1300 cfm ??? how can this house not be leaky ? I observed in the attic that the gable vents were sealed closed ?  can it be that?

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Unless my math is wrong I'm coming up with about 7.5 ACH50 (assumed 8ft ceilings). This doesn't seem out of the realm of possibility.
What ring were you using? This is a relative small house?
a1. I got to 50 pa on open and questioned why is it blowing sooo low, so I put in the A1 ring and got a similar number.

On small houses that you believe to be not too leaky, you should try using ring b or c.  Using the fan in the open mode or with ring a is usually for larger houses and/or leakier ones.

You need to experiment a little, don't be afraid to.  If you are using the blower door system from Energy Conservatory, they provide a very good/comprehensive manual with the system or even online on their website.  Check it out.

When you say that the house was recently redone, what was done in the way of tightening the envelope and insulation?  Did they seal the sill plates and rim joists?  How about the top plates of the walls in the attic?  Are there open soffits?  Ridge vent?  Passive or mechanical vent in the attic? How many exhaust fans and are they venting to the exterior?  Are all the doors and windows sealed well with weatherstrip and caulk and did they use low expanding spray foam around window and door frames when they were replaced?
No, I don't think contractors and their workers are that knowledgable here in so cal. No insulation anywhere. They were having electrical issue, the hvac blew the fuse some lights worked some didn't. They have not yet moved in. New windows, yes, they don't know if they sealed the windows or not. I don't think there was any air into the attic that must be boiling in the summer

 

It's just a simple small box of a house.  Not that big and only one story, no nooks and crannies.  If it has good windows and a good plaster or drywall job, and as you said laminated floors, and it lacks attic ventilation to code, then it is not surprising that it is relatively tight.  Open up those gable vents and vent the attic to code, and I bet you will get a higher leakage number, but it might not be much more.   

 

Small simple square salt box or cape cod type homes don't leak that much.  Multi-story homes and homes with more complicated architecture leak a lot more. 

 

If you do a good job on this house you will get it pretty tight so better plan for mechanical ventilation, and plan to upgrade any natural drafting combustion appliances. 

 

Thank you for the most simpliest of explanations. I am new to this field of auditing, so speaking in laymen terms is easier to understand.
+1. well said.

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