door blower test- do I need it?

[klk]

Since I now have had 3 different contractors over to give bids on replacing my 2- 20 yr. old systems ( a 3 ton & 4 ton)
Not ONE offered to do a Manual J( even though it is required for the NJ state rebate) -Do you think I should have a door blower test done and what exactly does it show?
Should I have an outside consultant come over and do the manual J and the door blower test-Since the house is 20 yrs. old- If so how do I go about finding such a person and how much approx. should it cost-Since we are going to be here a long time I want it done right- Everyone just asks are you comfortable now and then says just replace with the same size- Also a side question- The flex tubing from the handler to the ducts are starting to peel showing the insulation under it- 1 guy said you need to replace it and the others did not even mention it- Should I replace the flex tube or is it OK to have the insulation showing??- thanks for your help and sorry for the long post

[wayner211]

If it is required to do a manuall J load calculation then you need to find someone to do it. Another thing is just because you are comfortable now doesn't mean your system is sized correctly. I really recommend a load calc. and you also need to replace the flex pipe that is showing the insulation.

[klk]

Thanks - Is a door blower test something I should also do?

[wayner211]

I haven't ever heard of that type of test. That may be something required where you live. I am in Indiana and I have never heard of such a thing but definately do the load calc. and replace the flex.

[dash]

It's an excellant thing to have done.It can show you the duct leakage and infiltration rate,they would normally recommend duct repairs and improvements to reduce infiltration,if either are high.

[davidr]

A blower door is a great tool for diagnosing building envelope issues & infiltration rates, that is where it should stop though.

I would not recommend it be used for duct leakage testing, it is a misapplication of the blower doors design intent.

If you are interested in having your ductwork tested be sure the contractor you choose uses tools that are designed to actually measure airflow from HVAC systems.

[dash]

davidr,

Blower door is commonly used by major utilites,etc. ,for duct leakage detection.Can you explain why you think it shouldn't be.


I know ther are better ways,like http://www.aeroseal.com and duct blaster.but i think a blower door is fine.

[davidr]

Originally posted by dash
davidr,

Blower door is commonly used by major utilites,etc. ,for duct leakage detection.Can you explain why you think it shouldn't be.

For detecting leaks I have no issues, it is when they try to quantify leakage of CFM values with the blower door test.

The utility companies around here do a blower door subtraction test & use this to deem wether duct systems are efficient, not doing their customers much of a service.

Tight ducts are only one aspect of a properly designed system & have been focused on too heavily by the BS guys,I am preaching to the choir here though dash.

I am going to throw in something else here,I also don't trust a duct blaster either.

[dash]

We find the dcut blaster to be accurate,what is it you have found.

[davidr]

I am not personally big on the idea of using a fan that is foreign to the system to determine ductwork efficiency as some are using it.

When it comes to using a fog machine combined with a duct blaster it can really show some interesting results, a great visual aid

I am not putting these tools down, I am simply stating they should be used in the manner they were originally designed for.

In what manner are you finding it accurate dash?

[dash]

We use the Aeroseal process,which is really a duct blaster with the ability to inject sealent.

When the final cfm on leakage is determined ,after the sealing process,we find that testing with a flowhood ,and another dcublaster ,to leakage all comes out about the same. For the flowhood it's as compared to the TESP and the fan data sheet.

[davidr]

That is something I find very interesting dash considering the way both test methods vary in how they are performed.

Have you been using a fog machine with your duct blaster?

[dash]

No fog needed as we will use Aerosealto seal the leaks.