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: 323

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

Videos

  • Add Videos
  • View All

Twitter

Latest Activity

Luis Imery added a discussion to the group Job Board
Thumbnail

Hiring: Construction Manager with High Performance Custom Home Experience

POSITION DESCRIPTIONJob Title: Construction ManagerDepartment: Construction –…See More
11 hours ago
Profile IconLuis Imery and Quinn Korzeniecki joined Diane Chojnowski's group
Thumbnail

Job Board

This group is for posting jobs related to all aspects of the home performance industry including…See More
11 hours ago
Colin Genge posted an event

Retrotec is attending the NEBB Testing and Balancing (Tab) Certified Professional Review Seminar in Chicago, IL at Hilton Chicago O’Hare Airport

June 6, 2016 at 8am to June 8, 2016 at 5pm
Building owners and tenants are concerned that the environmental performance of buildings must be…See More
15 hours ago
Colin Genge updated an event
Thumbnail

Retrotec is exhibiting at the NFPA Conference & Expo-Booth 1355 at Mandalay Bay Convention Center

June 13, 2016 at 8am to June 16, 2016 at 5pm
NFPA's Conference & Expo is widely regarded as the most comprehensive industry event for…See More
15 hours ago
Tom White posted a video

Hayward Healthy Home Principles and Products

Bill Hayward discusses the principles that were used to build the first Hayward Healthy Home and how the products were evaluated for toxicity before they wer...
16 hours ago
Tom White's video was featured

Building Science Insights -- To Vent or Not to Vent

Building Science Presentation with Dr. Joseph Lstiburek.
17 hours ago
Quinn Korzeniecki added a discussion to the group Job Board
17 hours ago
Profile IconIan Smith, Brett Slezak, Autumn Secrest and 6 more joined Home Energy Pros
18 hours ago

© 2016   Created by Lawrence Berkeley National Laboratory.   Powered by

Badges  |  Report an Issue  |  Terms of Service