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: 197

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

Christopher Morin's blog post was featured

5 Things New Energy Efficiency HVAC Contractors Need to Know

1. Do not sell on Price! Use 'Simple Payback'The price of High-efficient equipment will undoubtedly…See More
2 hours ago
Jim Gunshinan's blog post was featured
2 hours ago
Profile IconDan Liska and Rob Moreno joined Home Energy Pros
2 hours ago
Jim Gunshinan posted a blog post
5 hours ago
Kim Tanner commented on Diane Chojnowski's group Home Energy Pros on Twitter
"Follow The Energy Conservatory on Twitter! We'll follow…"
8 hours ago
Kim Tanner joined Diane Chojnowski's group
Thumbnail

Home Energy Pros on Twitter

We've created a twitter list of members of Home Energy Pros who tweet!See More
8 hours ago
Bud Poll replied to Kaushal Bharath Raju's discussion Affordability & Deep Energy Upgrade/Passive House Retrofit in Berkeley, California.
"Hi Kaushal, First step is to understand where you are in terms of energy costs.  If current…"
11 hours ago
Kaushal Bharath Raju posted a discussion

Affordability & Deep Energy Upgrade/Passive House Retrofit in Berkeley, California.

We have a small 1940s single level house (1005sqf) in Berkeley, California that is in need of a…See More
18 hours ago
Christopher Morin posted a blog post

5 Things New Energy Efficiency HVAC Contractors Need to Know

1. Do not sell on Price! Use 'Simple Payback'The price of High-efficient equipment will undoubtedly…See More
23 hours ago
David Eggleton commented on David Eggleton's group Considering Permaculture &/or Transition
"In August 2014, in Minnesota, there's another unprecedented opportunity to meet and mix with a…"
yesterday
Glen Gallo commented on Jim Gunshinan's blog post Energy Upgrade California—Up Close and Personal
"Nate, RE: Duct test On my own home and a rental I have tested more than once over the last many…"
yesterday
Profile Iconangela hines and Charles Goldman joined Home Energy Pros
yesterday

© 2014   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service