Replies

1. 
   user-2310254 | Dec 05, 2019 01:23pm | #1

   Shige,

   If you search the site for advice on building "a pretty good house," you will find a lot of common sense advice. That said, I think you need to tell us more about what your full remodel will entail. Are you going down to the studs? Will you be replacing the roof and siding? How limited is your budget? If you are in San Jose, you are probably already spending a chunk of change for your home.

2. 
   typeshige | Dec 05, 2019 02:52pm | #2

   Hi Steve,

   Thank you, I'll start searching.

   I'm happy to provide more details!

   We are already down to the studs. The house had stucco, but it was installed on paper over the studs. So we already sheathed it in OSB and have the paper and wire with just the scratch coat so far.

   My current GC says it more air sealing should have been done when the OSB was installed, but that ship has sailed.

   So the house has just standard new windows and the start of stucco.

   The roof is from 2015.

   We have a GC that's almost ready to start. We are waiting for the construction loan to come in.

   But we need to do electrical, plumbing, insulation, hvac before the walls can be closed up.

   Framing is 2x4 on exterior walls.

   Winters get down to high 30s typically. Summers mid-90s. Occasionally below freezeing and a few days above 100. Lots of older houses here do not have any insulation and many don't have AC.

   I want to pick all the right products for insulation and hvac. We need to consider subflooring insulation as well as insulation in the attic.

   Looking for the best bag for the buck that is reasonably green.

   The GC has done a lot of houses and he knows what has worked, but I wanted to be knowledgeable about this so I can make sure we're getting the right stuff.

   For example, for AC, he was going to propose a standard furnace/central air.

   I asked him to look at the ducted Mitsubishi heat pump but he said his contractors are more familiar with the mini-splits.

   He said he heard Unico is better than Mitisubishi but my research on this site seems to imply maybe the opposite. Since all the walls and ceilings are open, I don't think Unico's small diameter ducts would outweigh its potential downsides.

   I'm curious if I could add ventilation as well.

   So I'm eager to keep learning and maybe find a like-minded installer in my area that can work with the GC on my full remodel.

   Thanks again!

3. Expert Member
   Dana Dorsett | Dec 05, 2019 04:22pm | #3

   >"we already sheathed it in OSB and have the paper and wire with just the scratch coat so far."

   I guess the continuous exterior insulation ship has already sailed too... :-( Even in San Jose 3/4" of continuous foil faced polyiso between the OSB and vented underlayment for the scratch coat would have been pretty cost effective, and protective of the structural wood. Continuous insulation on the interior side can work, but low-permeance foam board on the interior is risky when the cladding is stucco.

   Dense packing the 2x4 framing with cellulose to 2.8-3.2lbs per cubic pound density, or using cellulose or cotton batts would be the greenest:

   https://materialspalette.org/wp-content/uploads/2018/08/CSMP-Insulation_090919-01.png

   It would also be the most protective of the structural wood, now that there isn't a big cavity for the stucco to dry into.

   The center-cavity R would be about R13- lower than R15 fiberglass or rock wool batts (or dense packed fiberglass), but there is a modest performance boost in your climate due to the higher thermal mass or thermal diffusivity of cellulose or cotton vs. mineral or glass fiber. Cellulose in the cavities will buffer substantial amounts of moisture from the high moisture drives of reservoir claddings such as stucco, sharing the moisture burden with the structural wood.

   R13-R15 doesn't even hit IRC code minimum for IECC zone 3C, but might somehow might be allowed as a retrofit under CA Title 24 (?). The IRC calls out R20 (if cavity only), or R13 (cavity) + R5 continuous insulation.

   Building out the studs by 1.5" on the interior for greater depth and higher R could work, using Bongfiglioli strips, but it's a bit labor intensive and takes up a bit of floor area:

   https://www.finehomebuilding.com/membership/pdf/9750/021250059.pdf

   At 5.0" cavity depth the cellulose would be about R18.5, but with R5 (3/4" polyiso strips on 3/4" thick furring) the framing fraction's R-value would be nearly doubled, and the assembly would slightly outperform a 2x6/R20 or R13 + R5.c.i solution, and would meet IRC code on a U-factor basis.

   >"I want to pick all the right products for insulation and hvac. We need to consider subflooring insulation as well as insulation in the attic."

   Again, blown cellulose (1.2-1.8lbs density) is the greenest, and quite effective. The IRC calls out R49, but depending on the ceiling joist depths settling for R38 wouldn't be terrible, which would be about 11" deep (initial depth). A 2x12 is 11.25" deep- and there needs to be a minimum of 1" clearance to the roof deck, so it could be a squeaker to get it that deep full over the top plates of the exterior walls, especially if the joists are 2x10s, and probably impossible if 2x8s.

   If the house is on a full basement or crawlspace it's generally more effective and safer from a moisture perspective to insulate the foundation walls than insulating the subfloor. Describe what's under the subfloor.

   >"I asked him to look at the ducted Mitsubishi heat pump but he said his contractors are more familiar with the mini-splits.

   He said he heard Unico is better than Mitisubishi but my research on this site seems to imply maybe the opposite. Since all the walls and ceilings are open, I don't think Unico's small diameter ducts would outweigh its potential downsides."

   A RIGHT SIZED mini-ducted Fujitsu is probably a better bet than a ductless Mitsubishi or micro-ducted Unico solution. Any HVAC contractor who deals with small gas furnaces and split AC systems shouldn't have any problems designing duct systems for Fujitsu's xx RLGX series heat pumps, and they come in half-ton increments from 1-ton through 4 tons. With a proper load calculation it's possible to optimally right-size them. Most "normal" sized 1970 vintage houses in San Jose won't need more than a 2 ton, many won't need more than 1.5 ton, if the building envelope is up to current IRC standards.

   There are smaller and somewhat more efficient mini-duct cassettes from Fujitsu and others, but with less powerful blowers. HVAC hacks who haven't done the real math since they were in trade school will be more comfortable designing around the AOU/ARU xxRLGX series. The 1.5 tonner would have most 1800-2000' houses in San Jose fully covered with margin for those few sub-freezing hours per decade:

   https://neep-ashp-prod.herokuapp.com/#!/product/25348

   Have a third party (not an HVAC contractor) run the Manual-J load numbers, using aggressive assumptions on air tightness and R-values. Be sure they calculate the U-factors of any non-standard construction (such as Bonfiglioli strips) rather than taking a WAG at something that might be "close enough" in some pull-down menu on the load calculation tool.

   >"I'm curious if I could add ventilation as well."

   Of course you could, and should! But it's better to use a right-sized heat recovery ventilation system with its own (much smaller) ducts than trying to marry it to the heating/cooling system.

4. 
   user-2310254 | Dec 05, 2019 05:04pm | #4

   Shige,

   With everything opened up, you could cost out using AeroBarrier to tighten the structure.

   For ventilation, something like the Panasonic IntelliBalance might be a good fit.

   Hopefully, your GC is knowledgeable about best practices for creating a pretty good house. If not, you will have a hard time trying to backstop him on a project with so many moving pieces.

5. 
   typeshige | Dec 05, 2019 09:48pm | #5

   Thank you all for the wealth of information!! There are lots of leads to follow up on.

   It looks like I might be too late on things but I hope there is still hope to get the rest done right.

   I'll keep reading and learning!