Buildings Coping With Heat, Sans AC

Today as I write this, it's barely after noon and already close to 100 degrees, which we should surpass later this afternoon.

Most reading this are in air-conditioned buildings, while a few are toughing it out elsewhere. I work from home, and aside from a small window AC in the bedroom, I'm facing the heat without artificial air. I say this not proudly, but with lament. Still, I have a nice alternative I can take advantage of: the basement.

A basement is something hardly any new homes seem to have. I guess they're more expensive to build because there's the extra digging. But it's quite comfortable down here, even on the worst of heat days. Particularly if a home doesn't have AC or a heat pump, thus depending natural ventilation, I'd think surviving the summer would be worth the extra digging or expense, don't you?

Incidentally, I'm curious if there are architects or others enduring the heat today in green buildings with natural ventilation and no AC. How is your space holding up? When I've heard sustainable design enthusiasts talk about using things like thermal mass from concrete, thermal white membranes on the roof, exterior shading and all that stuff, it sounds great - until you get to a 100-degree day. Can any building without AC, no matter how green its design and materials, survive comfortably when we hit the century mark?

Comments

[george]

no exotic materials at my house. just a walnut tree and a cedar tree to my south combined with a new insulated home/vinyl windows/hardi plank siding. i can get thru a 100 degree day without breaking the high 70's inside at worst.

that is, as long as it gets down to 60 or so at night. last summer the evening after the 105 day only got down to about 80 so the next day was a big rough.

[Agustin Enriquez V]

We typically have the windows open and the AC off at GBD Architects (our office is in Brewery Block a space we designed to the LEED Silver level a few years ago). With the cross ventilation windows on the East side of our space, the temperature isn't a problem within 20'-30' of the window. The challenge is if you have one of the stations deeper in the core and don't get much of the breeze (we also have open work stations and the only "office" space is for the accounting department and that tends to help).

Unfortunately, after 100 degrees, it becomes less comfortable for those away from the windows and on those few days it cracks the century mark we are more likely than not to turn the AC on for a few hours after lunch.

Perhaps a better strategy would be to keep the windows open and institute a shorts and tank tops dress code on days where the temperature approaches three digits... or free popsicles if you're unlucky enough to be +30' from a window.

[Brian Libby]

How much could it help to be near a window when the air coming in is 100 degrees?

Also, this reminds me of something I've often thought about air systems. Why can't we build and make standard AC systems that also use and distribute fresh outside air whenever able? This obviously wouldn't be the case on a 100-degree day, but if you are in a building without operable windows, and since there's an air delivery system for AC air anyway, why can't that system be made to switch back and forth more effortlessly between refrigerated and outside air? Seems to me like buildings with sealed environments (no operable windows or open doors) could save a lot of energy that way on most days.

[Agustin Enriquez V]

It makes a huge difference. Temperature is only one factor that contributes to human comfort level. Think about the last time you were outside and standing directly in the sun without a breeze versus standing in the sun with a breeze. The outside air temperature is constant in both those cases, but your comfort level is markedly different. Mechanical engineers refer to psychometric charts regularly to determine how much cool air needs to be delievered to a space given air temperature vs wind speed.

[Tim]

Using an enthalpy wheel, energy recovery ventilators are an efficient way of supplying outside air and swapping its heat into the outgoing exhaust air stream to not overheat a space. Not that they are less expensive than AC units... These work great in conjunction with naturally ventilated buildings, as they can be told to come on only during certain times - such as when the CO2 levels exceed a certain level and when the temperature is over a certain level (when you would have the natural ventilation openings closed). They also work well in the winter, keeping heat in the space instead of exhausting it directly out. When you are trying to avoid having a building-wide ducted air movement system with an energy- hogging HVAC unit on the roof, this is the way to go, especially for classroom type buildings where each classroom would get one of these units above the ceiling.

[chris]

Is there any data on "green roofs" and their cooling effectiveness?

[Barney O'Donnell]

I live in a 1912 house in NE Portland. It has large eves and a cool, almost cold, basement. It takes about 4 days of 100 degrees to get the basement warm. Somebody must have designed it with summer in mind.

[crow]

brian. most buildings in portland utilize almost 100% outside air in their mechanical systems to reduce cooling loads / electric loads. we are lucky to have such low temperatures that the outside air is usually below a mean 60 degrees. Thermal mass, and night flush are very effective in offsetting the temperature swing just enough to make sure the occupants are out of the building before the temp gets too high - into the triple digits as you mention. As well stack ventilation as in the case of the exit stairs at OHSU - Center for Health and Healing by GBD architects is a very pleasant space to be in b/c the stack effect actually pulls cool air upward and helps create drafts which in turn makes the space very pleasant. This only works when you have a system smart enough to open up at the right place at the right time to create this draw of air upward to exhaust hot air and bring in cool air. You mention heat pumps, but another method is to use ground source where you plumb your water into the earth creating a loop - like the basement - going down helps to dissipate the heat into the ground before coming back up a cooler temp. The temperature about 10 feet below the ground is at a rather stable temperature.

[Greg]

I remember reading something about how you have to dig below the deepest point where the ground freezes. This is deeper in the midwest and northeast so it is more economical to build a basement there than here in the west. But I'm curious why many of the older homes here have basements?

[Convolooted]

Greg,

Yes, footings have to bear on soil that is below the frost line, which means that foundations have to be deeper in colder climates and by the time you have excavated for your footings you are halfway home to having a basement...might as well keep digging.

I can't say for sure why older homes have basements or cellars, but I suppose if you think back to the days before electrical refrigeration was in every house (prior to the late 20's and early 30's), the storing of root vegetables, preserved food items, and the like was probably a primary reason to have a basement.

[Joan]

As an architect working on a post-professional Masters, I am directing my thesis study towards the use of operable windows and natural ventilation in office spaces, and how the ambient urban sounds affect worker well-being.

I would also be interested in coming up to Portland from Eugene to explore this further.

Can anyone offer me any feedback on this topic?

[Brian Libby]

Joan, I'd recommend getting in touch with the BetterBricks Integrated Design Lab in Portland. They also have them in Eugene.

BetterBricks is a sponsor of this site, but I'm recommending you get in touch with their Design Lab because it sounds like the best fit for what you're looking for.