EVALUATING HOMES FOR COLD CLIMATE RESILIENCE

What parts of the homes in Texas would have benefited the most by providing for colder climate zones?

As a follow up to last week’s post re climate zones and how we build our homes, I wanted to compare how most homes in Texas would fair with homes built in a colder climate zone-say up in Ohio. This is purely from an insulation perspective for the house’s envelope (roof, walls, etc). I did not add doors and windows since there is a small difference there.

RESULTS OF THE COMPARISON

It seems there is not a lot of difference between how we treat the envelope of a house in Texas, to a house in Nebraska, with regards to how much insulation we provide. Those closer to the coast would have some adjustments to make, but not by a lot.

Below is a quick comparison of code required insulation from the Gulf coast of Texas (climate zone 2), to the northern tip of Texas (climate zone 4) and then a sample of what it takes to meet reqts for the next zone, climate zone 5. This is based on the code reqts for 2015, since that is what is most common in Texas.

WOOD FRAMED WALL INSULATION
Gulf coast (climate zone 2) = R13
North Texas (climate zone 4) = R20
Climate zone 5 = R20

ROOF-CEILING INSULATION
Gulf coast (climate zone 2) = R38
North Texas (climate zone 4) = R49
Climate zone 5 = R49

FLOOR INSULATION
Gulf coast (climate zone 2) = R13
North Texas (climate zone 4) = R19
Climate zone 5 = R30

SLAB INSULATION
Gulf coast (climate zone 2) = 0
North Texas (climate zone 4) = R10 for the depth of the footing or 2ft, whichever is less
Climate zone 5 = R10 for the depth of the footing or 2ft, whichever is less

CRAWL SPACE INSULATION
Gulf coast (climate zone 2) = 0
North Texas (climate zone 4) = R10 for a distance of 13 ft around the house perimeter
Climate zone 5 = R15 for a distance of 19 ft around the house perimeter

Either design it (crawl space plumbing) so it is easy to access and causes less damage on failure, or move the kitchen/bathroom so it is in a more sheltered location from your dominant winter wind.

A note on crawl spaces:
Notice the crawl space insulation, as we have a few of those here in Texas. I am sure we would prefer to have our entire crawlspace insulated, not just the 19ft around the perimeter-if cost was not an issue. This is one where you weigh the cost and benefits of it. From the damages we saw in this Texas freeze, I think we should pay extra attention to our plumbing lines that are in this area. Yes, we insulate these already-but did we not still see plumbing pipe damages in those same insulated, unheated spaces? These heated spaces became unheated when we lost power.

I have heard a few people lean towards using heat trace on these locations, however from my experience heat trace tape fails at the worst time and you find out about this failure in the worst way. If you can use heat trace, go ahead, but I would feel better if I could double up on that insulation anyway. Further more, I would design the house so that I can reduce the risks of this crawl space plumbing from damage. Either design it so it is easy to access and causes less damage on failure, or move the kitchen/bathroom so it is in a more sheltered location from your dominant winter wind.

MOST HOMES (45%) IN TEXAS – A CLOSER LOOK

Looking back at that climate zone map, about half of Texas is designated as zone 3. If you are in zone 3, then there may be a case made for having you or your architect design for zone 4. There is more difference between 3 to 4, than there is between 4 to 5. And since around 45% of the state of Texas is in zone 3, that may be worth considering. This is from a personal perspective, I do not wish for homes to be mandated by code to increase requirements. I am just sharing what is currently required so that a future homeowner can read the data and make their own decision should they have concerns about a colder environment.

Below is what you would need to meet to get a house that is in climate zone 3, to meet climate zone 4

WOOD FRAMED WALL INSULATION (same)
(climate zone 3) = R20
North Texas (climate zone 4) = R20

ROOF – CEILING INSULATION
(climate zone 3) = R38
North Texas (climate zone 4) = R49

FLOOR INSULATION (same)
(climate zone 3) = R19
North Texas (climate zone 4) = R19

SLAB INSULATION
(climate zone 3) = 0
North Texas (climate zone 4) = R10 for the depth of the footing or 2ft, whichever is less

CRAWL SPACE INSULATION
(climate zone 3) = R5 for a distance of 13 ft around the house perimeter
North Texas (climate zone 4) = R10 for a distance of 13 ft around the house perimeter

RESULTS OF THIS CLOSER LOOK

If you look through these, one of the big differences are on how we insulate exterior horizontal areas like your slab, crawl space and roof. Doesn’t that make sense compared to the damages we saw during this Texas freeze?

Maybe your roof was not an issue – upgrading that would pay off better in the summer than in a winter freeze anyway. But was not your perimeter slab one of the more painfully cold parts of your home when you lost heating? Homes in 45% of TX are in zone 3 and do not need to insulate their perimeter slab. If you have a crawlspace, you only had to provide R5 insulation if you are in this part of the state. What is the cost premium to increase you to R10 and does that math pay off for you?

CHECKING YOUR CLIMATE ZONE

Here is a link where you can check what climate zone your county is in. Scroll about 1/4 of the way down past all the other code references and get to the Texas counties. I must note again that this climate zone is for the Energy Code, not the USDA planting zone.

CLIMATE ZONE BY COUNTY (SCROLL DOWN TO ABOUT 1/4 OF THE PAGE DOWN TO TEXAS)

From here, I leave it to you as the home owner. You can take a look and see if the increase is worth it for you, should we face a colder future. There’s a juggle here on how much it costs, what benefits you get and how much of that can you do so that you get the most benefits.

Again, I am not advocating any more building codes. I am not fond of them myself. I am just using existing requirements as a reference since our existing homes were built to meet these already-and we can look and see how these homes performed in this colder climate.


Alt-Ark‘s goal is to make architecture more permaculture. We seek to empower the creation of forever homes that families can design to match the lives they choose.