I have a flat roof home with 3 feet of clearance from attic floor to ceiling. It is 1920 square feet, existing home. The space is unvented, and has one access hatch. It is in the master bedroom closet with no close access to a window or door. We plan to spray foam the roof deck. I am struggling to figure out how to ventilate the space during the job without positively pressurizing the attic. The home is stucco, so we do not have an easy way to create a hole to the outside. I typically rent a manhole fan. We can't suck air out of the hatch since overspray would ruin the rented fan (I think, maybe not?) When it is gables, I just leave the gable vents open(or mushrooms) until the very end of the job, and have the fan blow up into the attic hatch and out the gable ends. How do you spray foam guys ventilate an unvented attic space while spraying? We have just started on retrofit market, so most of our jobs have been new homes without these problems.

Views: 289

Reply to This

Replies to This Discussion

Hi Craig,

No direct experience in what you asked, but I have seen the venting process used for asbestos abatement.  In your case, an exhaust fan pulling through a large flex duct down through that hatch and extended as far as necessary.  I have a window fan that roars and I have used it to enhance an IR inspection when the blower door was not part of the consultation.  So even if the fan got contaminated, they aren't that expensive.  A round duct through a square hatch should leave plenty of room for fresh air.  Just thinking out load, good luck.

Bud

Bud - I think that is what we decided, except I will seal the exhaust fan in tight in the hatch, run a 20" flex duct to the outside. Keep a window open and allow the recessed cans to let air into the attic. If that isn't enough air we can always open a supply duct since the attic will be depressurized. Came down to finding the right combo of fan and duct. Can get both for around $100 total. I think the fans will hold up even with some overspray.

There are paper hoods that hook to your compressor hose.  Very slick and inexpensive.  Much better than counting on face masks. 

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

Colin Genge replied to billy g pinnick jr's discussion Blower Door Question
"I didn't take your comment as a challenge. I agree that his impression of what was occuring is…"
8 hours ago
Tom White posted a blog post

Clean Energy Works Oregon: Total Home Performance

Clean Energy Works Oregon (CEWO) is the largest nonprofit home performance provider in Oregon,…See More
11 hours ago
Tom White posted a video

Twas The Night Before a Clean Energy Christmas

From the foothills of the Rockies, RMI editorial director Pete Bronski reads 'Twas The Night Before a Clean Energy Christmas. Happy Holidays and Happy New Year!
11 hours ago
Chad Mcaulife commented on Green Jobs Training Center's photo
11 hours ago
Chie Kawahara's discussion was featured

THC Candidate Shares Energy Data

Midori Haus, a Passive House retrofit in Santa Cruz California and a Thousand Home Challenge…See More
11 hours ago
Bob Blanchette's discussion was featured

How does Cycles Per Hour affect real world AFUE?

Some claim that modern furnaces have minimized off cycle losses to the point they no longer matter.…See More
11 hours ago
Dale Stephens's blog post was featured

LED Lighting 24-month update 18,240 hours & counting

Background:In November 2012 I replaced 80% of my home's interior lighting with LEDs (35 bulbs…See More
11 hours ago
Home Energy Magazine's blog post was featured
11 hours ago

© 2014   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service