Will climate change cause a revision in building climate zones?
jackofalltrades777
| Posted in Building Code Questions on
With climate change, will this eventually cause a change in the current building zones are homes are located in? For example, if one is in a Zone4 climate, can that area become a Zone 5 or Zone 3, let’s say 20 years from now?
If so, shouldn’t we be designing that change into our building designs since there is a sort of a functionally obsolescence with those homes?
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Replies
I doubt very much climate will change enough to warrant a change in the zone maps in a 20 year time period. Remember that the predictions made 20 years ago about temperature changes never even came close to actually happening.
If there were to be sufficient changes I would imagine the zone maps would be changed for a future revision of the code. Codes are periodically revised to allow for new equipment and expierence, I see no reason why a “this map needs to be updated to better reflect actual weather data” update would be a problem.
I think it’s more prudent to insulate to keep energy consumption down and not worry as much about changing outdoor temperature patterns. Energy costs most certainly have increased in the past 20 years. If there were to be a change in weather patterns, you’re still covered.
Bill
Peter,
That's an interesting question. I wonder though - if the climate were to change enough to alter the zones, we would probably be facing so many difficulties, revising the codes might be low on our list of priorities.
I wouldn't worry much about temperatures. If you have good air sealing and insulation and good siting of the building, you should be okay. Same goes for water management: if you've got good overhangs, site grading, and flashing, you should be okay for more storms.
I would, OTOH, be more concerned about the spread of termites (ants should already be on your list of things to protect against), and I might be more interested in fire defense even though I'm not in what is currently considered a high fire risk area. This is strictly my opinion, but for those two reasons (bugs and fire), I'd favor mineral wool for exterior insulation.
A very interesting question.
I would imagine it will happen but what changes are hard to say, we simply can't predict the future with any accuracy.
That said the hazards of each time zone creeping into other zones is a reasonable guess. Higher R windows/walls/ceilings/floors are unlikely to be a problem if zones change then building an above code house will likely be helpful for future risks. Extreme weather is also more likely from tornadoes to high winds to flooding?
Can you build a house to withstand every climate zone without too much additional cost?
Peter,
Farmers and gardeners know that creeping climate zones are a reality now -- not just a hypothetical future event.
For builders, the biggest change (other than termite concerns for northern builders) will be the introduction of air conditioning in regions (like Vermont) where its use was quite rare until recently. This means that locations where interior polyethylene is still used might want to switch to a "smart" vapor retarder like MemBrain.
Interesting. Also if foam is used on the exterior with no vapour retarder (Toronto Canada) will the lack of vapour barrier matter if the summers get hotter and the winters colder?
Alan,
At least for now, Canadian building codes all require a vapour-barrier close to the interior.
So a diaper wall if you have exterior foam?
Yes in theory it's problem, but these types of walls (with what would under the recommendations for foam thickness recommended by GBA and others be too risky) have been the standard construction in Ontario and Quebec for a decade or more. When Building Science Corp looked at them they found no problems, as long as there wasn't a source or bulk water intrusion. Perhaps counter-intuitively, the reason these walls work is because they have a well-sealed interior vapour-barrier. The rate of drying through the foam is able to exceed the rate of wetting from the interior.
Apart for the building science aspect of all this, for now you still have to satisfy the code requirement for an interior VB. It doesn't have to be poly, but it does have to be something under 1 perm.
Climate change won't shift whole climates zones quickly enough to matter over the full lifecycle of a house, but will affect counties at the warm & cold edges even over the next 20 years. The DOE climate maps are based on county level weather statistics. With climate change some counties will end up colder, even as the global averages trend warmer, some counties (perhaps most) will be warmer, but none are going from the cold edge of zone 5 to the cold edge of zone 4 in the next 20 years, though it might in the next 80..
The error bars on the estimates 50 years out are too wide, to make accurate assessments of whether or when YOUR county will change zones in the next half-century, unless you're already at the zone boundary.
One case in point: Toronto weather data from the early part of the 20th century would put it at the warm edge of climate zone 6. But if looking at only the most recent 25 years it's definitely the cool edge of zone 5 now. It's already time to call it zone 5 now, no matter whose climate model you're using to predict climate over the lifecycle of a house built in 2018.
In 50 years Toronto may even be at the warm edge of zone 5, but it's too early to tell. Policy decisions & implementation between now and 2030 still have the ability to affect where Toronto ends up in the year 2100, but it's nearly impossible that it would end up in zone 7 or zone 4 in 2100. I would expect most of the homes built in Toronto this year will still be standing in 2100, and it's not risky to design to IRC prescriptives for either zone 5 or 6 (or 7) for a new house now, but would be quite risky to design for zone 4.
As timing/luck would have it, today Vox put up animated climate change maps for different US cities & regions showing the anticipated "equivalent climate" in 205o compared to the climate at another city's climate as of 1991:
https://www.vox.com/energy-and-environment/2018/11/30/18117953/climate-change-report-2018-cities-2050
Many of those will be a full DOE climate zone warmer than their current climate, but I didn't see any moving 2 full zones warmer, and some stayed within their climate zone, moving toward the warmer edge of the zone.
A King Tide flooded parts of Vancouver's seawall today yesterday. They are in the midst of an exercise to re-design their entire waterfront to take into account the anticipated rise in sea levels as climate change advances. I think Manhattan is doing similar work. It isn't just temperature rises and changes in climate zones that will affect how we build.