Wednesday, September 5, 2012

A Residence Attic Ventilation Review

This is continuation of posts of  November 30, 2010, December 15, 2010, and February 20, 2012. 
Please pick:

Another Really-Nice Job, Done 
Excellence Is Better Value 
Sealing With Three Times The Value Of Added Insulation 

My customer was served with the exceptional diligence I demand of myself. Yet, attic ventilation was not improved. The only ventilation is in the gable openings, about 90 sq in at each end of the attic, and that has been adequate. There are no mildew problems in this attic, even though the bath fan is not yet ducted through the roof. 

The soffits seem to have ventilation paths, and I did not have the courage or mandate as an insulation installer, to question this.

I dutifully baffled all roof joist bays, not knowing where vents might come through. There was no visible light.

With re-roofing imminent, I have questioned the contracted provision of added ventilation paths, two new static vent cans near roof peak. No one has yet taken responsibility for soffit vents. I now see that the holes in the vinyl soffit facia are tiny, and are fully blocked by wood structure. Soffit reconstruction is not feasible.

We are left, then, with the option I have imagined all along. For high-summer heat, rely on a solar-powered roof fan, and enlarged gable vents. Place the bigger gable vents symmetric if possible, and partially shutter them, to fully open only when the roof fan is operating. For the roof fan, I like the concept of Air Vent, Inc. with a PV array facing South, separate from a fan on the back side of the roof, North here. None of the involved elements are mature, and I hope to find more-suitable products in 2013. While waiting, there has been little summertime heat burden, due to thorough attic insulation.

If a re-roof must proceed before I am ready with powered-fan elements, I will instruct through the home owner, that there be no high roof cans. Such static vents lead purists to say that gable vents get confused, and should be blanked-off. The argument in this is stronger if a continuous roof peak vent is considered. I think I have a better handle on the big picture, and will confidently lead to have things my way. Retain and improve the gable vents.

This review is for information to the contracted roofer, for conversation with Joe Lstiburek, a no-gable-venting purist, and for inspiration of solar fan and gable louver manufacturers, who ARE part of the solution. Case in point.

And I might stand corrected. Air Vent Inc. reminds me there is another option for low air intake, SmartVent

I approach this as a skeptic. SmartVent claims 9 sq in per ft net free area, nfa9, through a load-supporting edge 3/4" thick. I think that is impossible.

Nfa9,  is needed here, at one sq ft per 150 sq ft house area, 60% for inlet paths, in a solution of static venting only, no gable vents.

Job Revisited, November 2013

There is a further post at February 2014, addressing wished-for innovation in design and installation of solar attic fans.

Sadly, I find that the roofer brought into this job has disregarded pleas that he not add static roof vents where they serve no inlet flow paths. There is NO air circulation from lower down, and the new roof vents clash in function, with existing gable vents. There is only one solution to this new problem. The home now must have solar powered fans, and they must occupy both new static vents. The gable vents will serve always as air inlets while the fans are running. This is the direction I wanted all along, but think this small house would be better served by a single solar powered fan. I contributed to this new dilemma by not finding a suitable fan in advance of the reroofing.


Kate Dunkin said...

Awesome post and review Phil! I came across your post while I was reading up on attic insulation , I'm happy i did because you shared very informative and interesting information with us when it comes to attic ventilation. Thank you for sharing this with us!

Keystone Contracting Corp. said...

Many families are oblivious to the amount of customization that they can do to their attics and roofs to alter the available climate year round, many ways including installing a solar fan, others, just opening up the roof a tiny bit to let some air in.

-Adam Ahmed
Roofing Brooklyn

Emily Freeman said...

I just wanna thank you for sharing your information and Stumblerz your site or blog this is simple but nice article I've ever seen i like it i learn something today.ilmanvaihto puhdistus

John Philips said...

Well done, it seems that you planned it well before doing it, I like the way you adopt some idea which make a nice result.

Ventilation systems