Sealing of Duct work joints in a sealed crawl space

[Robert Ellenberg]

I built my first sealed conditioned crawl space 5 years ago in a cold climate and have been sold on the concept ever since. I use a forced air HVAC system in the crawl space and it worked great and the floors were warm in winter without the expense of radiant heat.

Here is my question: I have not done the mastic sealing of ducts since they were in conditioned space. I have read all of the articles about why it is important and now that the codes are going to require pressure testing I assume I will have to seal them. However, a sealed conditioned crawl space requires a supply and return. It seems like a total waste to tightly seal the duct joints in the crawl space and then cut a hole in the side of the main supply and return at opposite ends of the crawl space.

Any thoughts?

 

[Bootleg]

Here in Washington State there are two ways to meet our new energy code.

Do a pressure test on the HVAC duct work if it is in unconditioned space.

Or

Do a blower door test at final.

 

[mtlogcabin]

In this climate ther are very few air conditioning installations therefore the crawlspace in not "conditioned" during the summer months. Traditionally the ductwork in the crawl space is sealed and uninsulated so the crawspace will be warm in the winter. Vent fans are installed that are controlled with a tempature humidistat switch to make sure the crawl is properly ventilated during non-heating months. There is plenty of leakage between the living space and the crawl that make up air for the vent fans is not a problem.

sealing the duct work and properly sizing the supply and return for the crawl is a better system than just letting it leak out where ever it can. You would notr heat your garage to 85 degrees why do you want to overheat a crawl space?

 

[Robert Ellenberg]

Thanks for the prompt feedback.

Bootleg, if I read your post correctly, either the duct work has to pass a leakage test or the house. If it is a choice of the builder, they seem enitirely different so is there an explanation as to why a tight duct system with a leaky house or a tight house with a leaky duct system is OK (or allowed)? I can see how they would choose one or the other or both as a requirment but why can it be one or the other of the owner/builders choice?

You don't over heat the crawl space but you are required to put a supply from the duct system into the crawl space so it is conditioned. It just seemed to me that tightly banded duct connections without mastic would allow some air in the crawl and probably enough to not require having a supply vent.

 

[Bootleg]

Robert,

We are just getting up to speed on the new energy code I did take a class last month.

How I understand it is the blower door and duct test is required at all SFR finals.

But you can have the duct system tested at framing inspection which I think is the best idea so you can correct any leaks.

Here's an e-mail I just received today, let me know if you have any questions and if it is any help.

Following is an information update from the WSU Extension Energy Program's Energy Code Technical Assistance Team.

________________________________________

Registration is now open for upcoming WSEC and Duct Testing Classes with the WSU Extension Energy Program. The following classes are now available:

• WSEC Training, Half Day - Kelso 7/27/10 sponsored by Cowlitz County. This is a half day training beginning at 9:00 am.

• Duct Testing - Kennewick 7/30/10 sponsored by the Homebuilders Association of Tri-Cities. his class will include a 3 hour classroom session where attendees will learn the new testing standard and how to operate the equipment necessary to test to this standard. The second half of the day will be in the field where participants will have the opportunity to operate the equipment and demonstrate their ability to run the test in a new construction scenario.

• WSEC Training, Full Day - Tacoma 8/26/10 sponsored by the MBA of Pierce County. This full day class will take place from 9:00 am until 4:00 pm.

For more details about these classes and to register for the classes visit the WSU Energy Code Support website:

http://www.energy.wsu.edu/apps/EnergyCode/2009EnergyCodeResources.aspx

________________________________________

Have Code Questions?

Residential building code support: energycode@energy.wsu.edu or 360-956-2042

Commercial or Non-Residential building code support: http://www.neec.net/energy-codes

________________________________________

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[Uncle Bob]

Bootleg,

"I understand it is the blower door and duct test is required at all SFR finals."

It that an I-code requirment or a Washington, State requirement. If IRC requirement would you please provide the section?

Ok, I found it in the 2009 IRC, Chapter 11, N1103.2.2. Either a post-consturction test or rough-in test. Not required by 2009 IRC.

thanks,

Uncle Bob

 

[peach]

might be in the IECC, UB.. but I don't think so... if the crawl space is conditioned all year round, who cares if the ducts leak (just like conditioned attic space, which you frequently see with foam insulation applied directly to the sheathing). It's adding conditioned to the already conditioned space.

 

[Bootleg]

Uncle Bob and Peach,

It's Washington State Energy Code.

 

[peach]

If the ductwork is in a conditioned space, is the blower door test still required, boot?

 

[Bootleg]

If the ductwork is in a conditioned space, is the blower door test still required, boot?

Yes peach,

Here in Washington State we require an air seal at framing inspection on all the exterior walls at top and bottom plates where they are drilled and seal the electrical gang boxes and under the bathtub.

So that is the reason for the blower door test at final inspection.

 

[ewenme]

In the IECC ['09], Visual inspection is an option for air sealing and insulation testing with a door blaster. [section 402.4.2.2] and there is an exception for duct blaster testing: Duct tightness test is not required if the air handler and all ducts are located within conditioned space. Section 403.2.2 Exception.

In our jurisdiction, we don't see many furnaces installed in conditioned space, and a lot of the ducts are installed in attics or crawlspaces, and therefore we'll be requiring the testing. To that end, I applied for and received a grant to do a duct blaster demonstration project, brought in a trainer and invited the contractors to learn 'how to' and 'why'. The City will have duct blaster equipment available for the contractors to set up, and will be required to invite the inspector to witness the tests. Some of the contractors are excited about the prospects [those that take pride in their work] and some contractors think this will be pure hell.

I wonder if house designs will change to reflect the 'need' to put the ducts/furnaces in conditioned space? And this is only the beginning, just wait until the 2012 IECC comes out with even more restrictions and energy saving requirements.

 

[peach]

The OP is talking about ducts in conditioned space.

Boot.. the sealing of top and bottom plates has been in the code forever.. fire blocking.

Energy conservation is a good thing; tight construction is not. So far, there isn't a happy balance.

 

[RJJ]

MT: I Have to agree! So many codes! So much confusion!

 

[peach]

A blower door test is different than a duct blaster test...