07-21-2020, 04:03 PM
(This post was last modified: 07-22-2020, 03:27 PM by dobanion.
Edit Reason: Removed comment about spammer
)
Original IECC 2015 (start with reading this): https://codes.iccsafe.org/content/IECC2015
Hawaii county started enforcing IECC 2015 compliance (without amendments) on August 15, 2019. Then, as of Feb 4, 2020, they published their official amendments. Follow the link below to the page and you can read through their amendments.
https://energy.hawaii.gov/wp-content/upl...gyCode.pdf
IECC compliance sheet is here:
http://records.hawaiicounty.gov/weblink/...ronic.aspx
In further discussion, I'm just calling Simulated Performance Alternative as SPA, getting tired of typing it out.
To expand on what I stated above, it would seem that my initial assumptions were wrong. Usually are. The fine print in the original 2015 IECC for the table for how to model the SPA basically says you need to include a basic air conditioner and heater in the model, even if you aren't going to use one. I see now the purpose of this. Without those, anything would go. It would always compare out as similar energy use. But they want to see that the house as modeled is as or more efficient than whatever they are calling for, and to do that, you need to model how much energy a AC unit would use on a annual basis, were you to stick one in a window. Makes sense.
So in my model, I had AC and heat. I entered in the climate model for Hilo (they have one for Kona too). When I ran the simulation, with the AC set to 73F, and the heat set to 68F, I got AC usage, but zero heat usage. If you were to install a electric furnace in a house in Hilo with the thermostat set to 68F, it would in all probability NEVER turn on. Model makes sense.
For the reference design you essentially do all the things that they have in the "prescriptive" approach. The big stuff:
Walls and roof have .75 absorption (means 75% of the energy that falls on them is absorbed). Most colors are in this range.
Ceiling or roof has R-30
Framed walls have R-13
"Mass" walls (ie concrete, be it block or otherwise) has R-4. This is not additional R-4, rather the wall itself must be R-4. According to the NREL software, a cinderblock wall is already R-5.
Floors do not need insulation, be it slab or post and pier. This is from the amended code, the original IECC 2015 did call for floor insulation on above grade floors (not slab). So, kudos to Hawaii county for that.
Now, for the house I'm designing, I use mass walls. So, I don't have to call for insulation in the walls of either my reference or my design.
When I switch from .75 to .3 absorption exterior surfaces (ie white metal roof and a bright exterior color), and I eliminate the R-30 in the roof, I end up with about 30% LOWER cooling energy usage on a annual basis. As it turns out, keeping the surface from absorbing the heat in the first place is a better approach than trying to keep the heat out with insulation.
This is the approach I plan to take in my permit application. I will also note this model is bound to stink if I needed to use a heater. This house wouldn't work in Volcano, for instance.
I tried this with a wood framed house as well. Now things change, because I'm required to use R-13 in my reference design walls. Now, it's a wash. The uninsulated/reflective house and the insulated/non-reflective house are nearly the same. It's so close I doubt you could convince anyone to approve it. But, if you either use some mylar in the attic, OR switch to the best roof paint I could find (Henry 887 Tropi-Cool at .15 absorption), that gives you a 8-10% margin. I didn't run the numbers with the super bright stuff on the walls, I know nobody is gonna do that.
Hawaii county started enforcing IECC 2015 compliance (without amendments) on August 15, 2019. Then, as of Feb 4, 2020, they published their official amendments. Follow the link below to the page and you can read through their amendments.
https://energy.hawaii.gov/wp-content/upl...gyCode.pdf
IECC compliance sheet is here:
http://records.hawaiicounty.gov/weblink/...ronic.aspx
In further discussion, I'm just calling Simulated Performance Alternative as SPA, getting tired of typing it out.
To expand on what I stated above, it would seem that my initial assumptions were wrong. Usually are. The fine print in the original 2015 IECC for the table for how to model the SPA basically says you need to include a basic air conditioner and heater in the model, even if you aren't going to use one. I see now the purpose of this. Without those, anything would go. It would always compare out as similar energy use. But they want to see that the house as modeled is as or more efficient than whatever they are calling for, and to do that, you need to model how much energy a AC unit would use on a annual basis, were you to stick one in a window. Makes sense.
So in my model, I had AC and heat. I entered in the climate model for Hilo (they have one for Kona too). When I ran the simulation, with the AC set to 73F, and the heat set to 68F, I got AC usage, but zero heat usage. If you were to install a electric furnace in a house in Hilo with the thermostat set to 68F, it would in all probability NEVER turn on. Model makes sense.
For the reference design you essentially do all the things that they have in the "prescriptive" approach. The big stuff:
Walls and roof have .75 absorption (means 75% of the energy that falls on them is absorbed). Most colors are in this range.
Ceiling or roof has R-30
Framed walls have R-13
"Mass" walls (ie concrete, be it block or otherwise) has R-4. This is not additional R-4, rather the wall itself must be R-4. According to the NREL software, a cinderblock wall is already R-5.
Floors do not need insulation, be it slab or post and pier. This is from the amended code, the original IECC 2015 did call for floor insulation on above grade floors (not slab). So, kudos to Hawaii county for that.
Now, for the house I'm designing, I use mass walls. So, I don't have to call for insulation in the walls of either my reference or my design.
When I switch from .75 to .3 absorption exterior surfaces (ie white metal roof and a bright exterior color), and I eliminate the R-30 in the roof, I end up with about 30% LOWER cooling energy usage on a annual basis. As it turns out, keeping the surface from absorbing the heat in the first place is a better approach than trying to keep the heat out with insulation.
This is the approach I plan to take in my permit application. I will also note this model is bound to stink if I needed to use a heater. This house wouldn't work in Volcano, for instance.
I tried this with a wood framed house as well. Now things change, because I'm required to use R-13 in my reference design walls. Now, it's a wash. The uninsulated/reflective house and the insulated/non-reflective house are nearly the same. It's so close I doubt you could convince anyone to approve it. But, if you either use some mylar in the attic, OR switch to the best roof paint I could find (Henry 887 Tropi-Cool at .15 absorption), that gives you a 8-10% margin. I didn't run the numbers with the super bright stuff on the walls, I know nobody is gonna do that.