I've encountered an install of 6" duct directly connected to the outside through the rim joist and covered by a simple mess screen on the end.  The other end has been placed next to the gas furnace as make-up air.  The cold air just pours in whether the furnace is active or not.  There is a clear need for make-up air as the CAZ is very small and the DHW and furnace are next within a couple of feet of each other.  Any advice on a simple mechanical option to better regulate this situation.  (The DHW is natural draft and the furnace is power-assist.  They are commonly vented.)   

Views: 223

Reply to This

Replies to This Discussion

Let it be known common venting of power draft and natural draft appliances is against code in many jurisdictions. Are the DWH and Furnace in conditioned or unconditioned space?

The units are in a conditioned laundry area, 16'X11'X7.5'  The DHW is 36K btu & furnace 45K btu. (Dryer is electric.)

Hi Jerry, your classic can of worms.

Each of us must decide where we will draw the line, that line where we can be blamed for making conditions worse and this is one.  Any improvements on air sealing could affect that CAZ, therefore, IMO, I advise the problems need to be fixed FIRST, before I will continue with an audit.  I usually catch these with a pre-audit visit, but that's my routine.

Here is some of what you face and I'm not a pro on HVAC as Maine prohibits auditors from doing anything beyond the specified CAZ test. 

1.  Venting as Bob mentioned needs to meet code.

2.  Replacement air also needs to meet code, such as vent area, high and low vents, and outside clearance.  A 6" duct is way too small.

3.  Any mechanical solutions need to be approved for that use, no shoe strings and cloths pins.

A common recommendation is a cold air trap with a bucket or a 180° turn in the incoming duct.  The short explanation is, they don't do as advertised and neither would bring the venting up to code.

Most burner units, and you have two, have combustion air kits that can draw air directly from the outside.  There are also powered dampers which open and close as needed and prevent the burner from coming on if they fail.  Whether either of these could be used to solve the problem and meet the codes would need to be determined.

Again, this is my opinion and perhaps others will chime in with some code requirements, beyond my scope.

Bud

Picture of uncontrolled make-up air duct next to furnace.

 

Attachments:

Glad they used insulated duct for the fresh air intake ;)

Have you considered sectioning off the water heater and furnace from the rest of the laundry area? Make the that unconditioned space. How about a vent between the laundry area and the rest of the house effectively increasing the size of the laundry room and eliminating the need for make up air?

Be sure to check local codes before making a final choice. As Bud said this may be a HVAC contractors issue, although I probably wouldn't call the one that stuck in the 6" flex for fresh air...

RSS

Home Energy Pros

Home Energy Pros was founded by the developers of Home Energy Saver Pro (sponsored by the U.S. Department of Energy,) and brought to you in partnership with Home Energy magazine.

Latest Activity

Profile IconEthan Bukowiec and Andy Li joined Home Energy Pros
5 minutes ago
Bob Blanchette replied to w d's discussion Managing Solar Energy
"Look into passive solar heating. The south windows have enough overhang that the windows are shaded…"
12 hours ago
Steve Waclo commented on Kaplan Clean Tech's blog post The Difference Between Home Inspection and Energy Auditing [Infographic]
"Excellent graphic summary but I don't agree Home Inspectors also check energy use. I believe…"
yesterday
Steve Waclo replied to Linda Wigington's discussion Low-cost electricity monitoring: Accuracy & Applications in the group 1000 Home Challenge
""The problem with plug in energy testers is they miss most of a typical homes energy use. 240v…"
yesterday
w d posted a discussion

Managing Solar Energy

What's the state of the art on managing solar energy (esp. at the home)?There's surely no…See More
yesterday
Bud Poll posted a discussion

Inconsistant Local Authotity

It becomes frustrating to give people modern advice and then have to backtrack and tell them to do…See More
yesterday
Morgan Hunter replied to Isaiah Borel's discussion Blown Cellulose VS Blown Fiberglass in the Attic
"Up here In Canada Fibreglass wins hands down for heat loss! Check back 5, 10 & 20 years later…"
yesterday
Bob Blanchette replied to Linda Wigington's discussion Low-cost electricity monitoring: Accuracy & Applications in the group 1000 Home Challenge
"The problem with plug in energy testers is they miss most of a typical homes energy use. 240v…"
Saturday

© 2014   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service