Comments on: Naked People Need Building Science

By: David Butler

David Butler — Sun, 08 Jan 2012 23:25:05 +0000

Ted, it only takes a few
Ted, it only takes a few degrees of difference for ceiling to become a radiant heater, so no, the ceiling doesn't need to be hot for a ceiling fan to provide this additional benefit.

Regarding winter use of fans, as I said, the benefit is small, but it's useful to understand why there's a benefit at all.

By: Ted

Ted — Sun, 08 Jan 2012 22:55:45 +0000

David/Chad - Claiming ceiling
David/Chad - Claiming ceiling fans are good for more than evaporative cooling requires case by case.

"Theoretically" it cools the ceiling - assumes the ceiling is hot which is often NEVER the case, certainly not ALWAYS the case.

"Theoretically" it mixes stratification. Given high delta heat sources are less and less common, this is legacy thinking much more appropriate to 1970's heating than 2012.

(I have a client who spray foamed his attic. When he heats with his oil furnace the house is colder the higher he gets, and the unintentionally conditioned attic temp is between home and outdoor temp. When he heats with his wood stove the reverse occurs. It get's warmer as he goes up with his unintentionally conditioned attic reaching sauna-like temperatures.)

By: David Butler

David Butler — Tue, 27 Dec 2011 01:58:28 +0000

Chad:
Chad: Granted, any winter benefit will be small, perhaps not worth talking about. But the idea is to ensure that the warm supply air from the registers reaches the ceiling. In the case of radiant heat, ceiling temperature may not be an issue, but a fan will help in a different way -- by disrupting stratification.

Personally, when in bed, I like to feel slight air movement on my head in the winter. But if air movement bothers you, then don't use a fan.

By: Chad

Chad — Mon, 26 Dec 2011 19:40:05 +0000

David B,

David B,

Interesting take on ceiling fans in winter... I hate any air movement in winter I don't care how slow the air speed is. When you reverse the fan doesn't it bring cool air from the floor up and cool the ceiling???

By: Allison Bailes

Allison Bailes — Tue, 13 Dec 2011 15:31:06 +0000
Thanks for all the great
Thanks for all the great comments. Just in case you're wondering, that's not me in the photo at the top. Evidently, some people suspected that it was. Nope. Just some random dude from flickr.com.

By: Debra Little

Debra Little — Tue, 13 Dec 2011 11:59:30 +0000
Sweeeet little home is almost
Sweeeet little home is almost as endearing as jumping jack flash.

By: Bean

Bean — Tue, 13 Dec 2011 01:57:46 +0000
JN: This Buds for you <
JN: This Buds for you an article on seniors, long term care and HVAC systems.

PJ: Deferring to a famous building scientist who said, “one can pick ones nose, pick ones teeth or scratch ones rear, and the significance of the order is not a trivial matter.” You are correct, upgraded and right or oversized HVAC equipment becomes oversized or more oversized when the building loads are reduced…the effects of said oversized equipment is the fodder for ongoing debates around the industry. Maybe Allison can expose this topic further...

JP: If you don’t mind waiting for the 120 second upload, see slide appx. 19 from this ASHRAE SAC Lecture , as you mentioned, it is exactly the analogy I use...great minds...

DB: A significant amount of our work lately on SSPC 55 is on elevated air speeds for thermal comfort in hot climates and naturally ventilated air spaces; and in fact there is a new graphic in the 55 Standard to illustrate these conditions. Also elevated air speeds have also been updated in the ASHRAE 55 Thermal Comfort Software Tool.

By: Bean

Bean — Tue, 13 Dec 2011 01:00:57 +0000
Allison,

Allison,

You have single handedly motivated all the nudists and all the wannabe nudists to collectively improve the performance of their homes AND finally brought equality to the three scantily clad tall Danish ladies who years ago participated in a large thermal comfort research project as recorded by the project photographers. I vote for the new slogan for thermal comfort - “Show your skin”!

...

On behalf of all those who get that air temperature is not a surrogate for thermal comfort, and get the principles of MRT and Operative Temperature – our hats (and shirts, pants and socks) are off in your honor of this new day.

Three cheers *** and a big thank you.

RB

By: John Mattson

John Mattson — Tue, 13 Dec 2011 00:30:08 +0000
Great example and article;
Great example and article; both amusing and informational. Please ignore the puritans and keep up the research.

By: David Butler

David Butler — Mon, 12 Dec 2011 23:05:27 +0000
Great article, Allison.
Great article, Allison. Ceiling fans help in summer, not only because they cause evaporative cooling of the skin, but also because they reduce the surface temperature of the ceiling. A slight reduction of the ceiling temperature will have a significant impact on radiant heat transfer to the body, especially when we're sprawled out horizontally in bed, with more of our surface area exposed to the ceiling. In winter, a ceiling fan will help increase the ceiling temperature. Just make sure to reverse the direction and use the lowest speed to prevent unwanted evaporative cooling.