Hi all, I'm looking for advice on how a Tucson home can be made more energy efficient.

They're 2x4 framing with fiberglass batt insulation in the walls and 1 inch foam on the outside. They claim R19 walls. Ducting is flexible insulated up in the attic trusses. Insulation on the roof is reported to be in the high 30's. They've started putting radiant barriers on, but not on the age house I want, and the roof is nicely done in ceramic tile. Can a radiant barrier be retrofitted>

Some of my thoughts are rip out the HVAC, sell it used and replace with heat exchanger mini splits. Then I could insulate in the trusses, maybe with a loose fill.

HRV will be investigated as well as window improvements.

I'll hope to buy based on sun path and proper solar gain/mitigation.

Any suggestions?

A radiant barrier can be retrofitted, and it's reasonably cost effective for your climate, but it's not any better than just adding more insulation. I'm not totally clear on where the R30 insulation in the roof/attic is now. But I like your idea to replace the HVAC with minisplits and add more insulation.

Another thing to consider is indirect evaporative cooling. The same "free" cooling as a swamp cooler without the humidity increase.

A key step will be a blower door test and to seal the air leaks you find.

Yea, where is the roof insulation located exactly? Is the attic sealed or vented I am not entirely convinced an IR barrier would do you that much good. Added to the attic space, what is it going to do but reflect the IR back against the inside of the roof, which is inside the space already. Unless that heat is vented or otherwise dealt with, it is still inside the attic space... I agree added insulation would be a equally effective(if not moreso), and IMO probably a better investment... Added insulation in and around those ducts in the attic would definitely be a plus.

Probably not much that can be done for the walls without a major overhaul.

Fully agree a blower door is in order which will show you where you are leaking and how much improvement the windows and doors might need. Infiltration can quickly dominate the HVAC equation. An HRV/ERV will definitely help, not only in recovering the conditioned energy, but in balancing the air pressure of the envelope and perhaps helping to reduce uncontrolled infiltration

The minisplits may or may not be a better idea, depending on the age and condition of the existing system...

Posted By chrs on 05 Oct 2015 10:06 PM
A radiant barrier can be retrofitted, and it's reasonably cost effective for your climate, but it's not any better than just adding more insulation. I'm not totally clear on where the R30 insulation in the roof/attic is now. But I like your idea to replace the HVAC with minisplits and add more insulation.

Another thing to consider is indirect evaporative cooling. The same "free" cooling as a swamp cooler without the humidity increase.

A key step will be a blower door test and to seal the air leaks you find.

Radiant barrier is substantially LESS cost effective than adding insulation in almost all cases.  Even if the attic is only insulated to IRC 2003 levels and has insultated ducts in the attic its hardly cost-effective on a net-present-value of future utility savings basis. See:

http://web.ornl.gov/sci/ees/etsd/bt...et2010.pdf

It only makes sense if there isn't space to install code-min or better attic insulation.

Getting the HVAC completely inside the thermal and pressure boundary of the house (and right-sizing it for the loads) does far more for both efficiency & comfort than any radiant barrier retrofit.

Thanks for all the advice. I would leave the radiant barrier alone, then. I would concentrate on the blower door and IR tests and sealing it up. Maybe thermal mass next and wait for the HVAC to develop problems to move towards mini-splits.