I have a client who needs your help. In the early 80's, he and his wife built a beautiful off-grid home on a small island near Fort Myers, FL. It currently serves as a convenient getaway, but as they approach retirement, they want to install a limited amount of air conditioning in the form of a couple of small, high-SEER ductless mini-splits.

The aging 12V PV system is quite small -- the refrigerator is propane powered, and there's no well (fresh water supplied by rainwater collection). So he's going to need to upgrade the power system to support the mini-splits. To keep costs reasonable, some envelope improvements are warranted.

It turns out, the gorilla in the room is the uninsulated metal roof. It's supported by beautiful site-built beam trusses and the exposed roof panels serve as a decorative ceiling. You can only imagine how hot that surface gets, making the home virtually uninhabitable for 4 or 5 months a year.

I'm not sure what's the best approach to insulate this roof. The owner wants to avoid pulling up the existing roof, which is seriously bolted down, successfully weathering Hurricanes Wilma & Charley and numerous tropical storms. Moreover, the owners have a strong preference for preserving the aesthetics of the exposed metal interior, which means working from above.

I'm thinking 4" of XPS or poly-iso covered by another metal over-roof. Keep in mind the roof serves as primary collector for fresh water so shingles are a no-go (aside from blow-off risk from the inevitable storms). However, I don't know enough about this to advise on attachment and edge details. Nor do I have a feel for cost, other than it seems obvious that working from below would be less expensive since it wouldn't be structural and he could use a less expensive insulation product.

I've attached several images for reference. I know we have some savvy retrofit gurus among the membership. I'd appreciate your advice!

Views: 1035

Attachments:

Reply to This

Replies to This Discussion

Bill, I was trying to keep a gap between the metal roof and insulation for air movement and to allow a cooler insulation on contact. I had a ureathane company for 13 years and cannot stress more strongly don't install it inside the envelope. The  distance between the 2 purlins compressing the foam with long screws staggered will transmit wind shear to original structure. Best of luck. PS. long screws have to be larger diameter for adequate shear transfer of wind loads ex.. 6" should be #14 at least.

RSS

Latest Activity

Stuart Langley liked David Byrnes's blog post Strategies for Hiring and Interviewing for Home Performance Professionals
2 hours ago
Kevin Miller replied to Bob Krell's discussion What Do You Do When You Find Suspected Mold? in the group Healthy Indoors (IAQ)
"Visual inspection can only confirm the presence of mold, not the absence.   That said,…"
5 hours ago
Armand C Magnelli replied to Don Fugler's discussion joining ducts in the group HVAC
"I often suggest pop-rivets as an alternative to sheet metal screws for both clothes dryer duct work…"
5 hours ago
Kevin Miller replied to Bob Krell's discussion What Do You Do When You Find Suspected Mold? in the group Healthy Indoors (IAQ)
"Sampling would be primarily to verify 'Condition 1' or 'Normal Fungal Ecology'…"
5 hours ago
Daniel Cullen joined Building Performance Institute's group
Thumbnail

Building Performance Institute (BPI)

BPI is the nation's premier standards development, quality assurance and credentialing organization…See More
5 hours ago
Daniel Cullen replied to Bob Krell's discussion What Do You Do When You Find Suspected Mold? in the group Healthy Indoors (IAQ)
"Can anyone tell me exactly HOW mold sampling impacts the mold remediation process or protocol? Why…"
5 hours ago
Daniel Cullen joined Bob Krell's group
Thumbnail

Healthy Indoors (IAQ)

The Healthy Indoors group is focused on indoor air quality (IAQ), mold, moisture control, radon,…See More
5 hours ago
Debra Little's video was featured

Robert Bean, Iain Walker, indoor environmental quality experts

Robert and Iain discuss home indoor health & environmental quality. Design for human factors; thermal comfort, air quality, sound, odor...kitchen exhaust, th...
6 hours ago

Photos

  • Add Photos
  • View All

© 2017   Created by Home Performance Coalition (HPC)   Powered by

Badges  |  Report an Issue  |  Terms of Service