Cold concrete

[ACFIXR]

I have a room that "feels" cold even when the temperature is 70 degrees. I think that this is from radiant loss from my skin to the floor. After combing through ManJ8 I learned that "Ceiling outlets are best for cooling, but will not warm slab or exposed floors during the winter."

http://i1201.photobucket.com/albums/bb359/Chuck_Phelan/stem_wall.jpg

The slab on this room is covered with a stone tile and elevated by a 24" stem wall that is exposed to the air on 50% of it's perimeter.My question is: Does Man J 8 have an F value for stem walls? Or does a stem wall effect the "F" value?
I think that a stem wall would help a slab dissipate heat at a faster rate.
I was trying to explain to the builder and home owner "why" the room fells cold even though the thermostat shows a comfortable temperature.
Any input would be appreciated.
I will be heading back to take a surface floor temperature soon,wasn't smart enough to do it while I was there.

[tipsrfine]

Check the humidity also.Obviously you want to verify t-stat temp is accurate also.

[Shophound]

Slab edge heat loss and gains are real factors, even in so called "warm" climates, like Tucson or where I live.

How much of that is from direct conductive loss or gain is worthy of study. What I've been personally doing in my own home, during cold months, is attempting to distinguish cooling of the floor from direct slab edge loss, proximity to a single pane window, and infiltration leakage at the sole plate of the framed wall.

Earlier this year I made a huge leap forward in reducing my home's air leakage rate. In cold weather, so far, this has translated to warmer floors than when the house leaked a lot more. While I'm confident the slab edge losses aren't changed, the decrease in air leakage via stack effect and wind has been noticable by my built-in measuring rod, my feet. Last winter my feet would get cold even with shoes on. Lately I've been able to be seated at my desk or dining table with just socks on my feet, and although cool it's not uncomfortably cool.

As indicated in my signature, and as you note in the OP, indoor comfort is not just via air temperature. Mean radiant temperature is something I don't think those of us in the comfort business pay enough attention to, although I think that's changing. Tips mentioned humidity, which is another large player in comfort. I would imagine in Tucson the indoor air in homes with a fair amount of leakage can become quite dry in winter, given how dry the outdoor air already is. This can make a person feel colder than the air temperature may indicate.

[hvacker]

One ? asked about stem walls is perimeter insulation on the stem wall and if the insulation extends away from the wall underground. If the wall isn't insulated at all the numbers get big. Another thing that wasn't done on my house is a thermal break between the slab and footing.
It's usually a strip of celotex running the length of the slab. I don't know if this was originally meant for slab expansion but the effect on slab temperature is noticeable.
I had no parameter insulation so two years ago I dug down below the footing and installed 2" of blue board below grade and up enough to cover the slab and footing. I also extended the blue board 18" away from my house below grade, Wired and stucco to finish. This was a good improvement.
Manual J does have F values for seem walls but they vary with soil type, insulation, grade level etc.
There are higher velocity grills than are found in homes available that might help.

[genduct]

There is this whole explanation about the average surface temps AND the air temp that the radiant people use to their advantage.
For instance the reverse is you can be comfortable with 65 degree air when the floor is 80 degrees.

[ACFIXR]

Slab edge heat loss and gains are real factors, even in so called "warm" climates, like Tucson or where I live.

As indicated in my signature, and as you note in the OP, indoor comfort is not just via air temperature. Mean radiant temperature is something I don't think those of us in the comfort business pay enough attention to, although I think that's changing.

This house just went through a complete re-model. The windows were upgraded to low-e and high SHGC's.All the plate penetrations were sealed and the can lights are tight.The duct work is all sealed and r-8 insulated.This room has brought me into learning again about radiant heat. I think that you hit it on the nail head with the mention of mean radiant temperature.
So basically the mean radiant temperature of a room is the average temperature of all the surfaces in the room proportional to the percentage of area that it encompasses. In other words the air temperature in the room is 70 degrees but the floor temp is 60 degrees therefore I feel like 65 degrees?
My choice then to improve comfort in this room is to heat the floor,add exterior insulation on the slab or throw a large carpet down.

[SolarMike]

as we all know, heat moves from hot to cold so as long as the slab is below body temp it WILL feel cold. Even a few degrees from solar panel or boiler will bring it close (assuming there is floor heating in it). I havent done a house in 20 years without a radiant floor in the slab, and slab edge insulation.

[ACFIXR]

Found this from an air expert about heating residential rooms with high supplies in ceilings.He basically suggests throwing the air across the ceiling with the register vanes then throwing it against the walls with a ceiling fan.The warm air then cascades down the wall to the floor.

http://www.krueger-hvac.com/lit/whitepaper.asp

What do you guys think?

[tipsrfine]

Which article is it you are referring to? That link opens up a main page with a bunch of articles listed.

[ACFIXR]

Sorry, wrong link.

Here is the one I was talking about;

http://krueger-hvac.blogspot.com/2011/12/heating-in-residential-applications.html?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+KruegersAirDistributionBlog+% 28Krueger%27s+Air+Distribution+Blog%29

And it works! Thanks Tips.

[Shophound]

This one deals with the subject in question, but is particularly addressing working with VAV boxes vs. a residential application:

http://www.krueger-hvac.com/lit/pdf/white_AJ_reheat.pdf

[skippedover]

If you want to experience what you're feeling somewhere other than in your living room, step outside on a 50°°F day. Now step into the shade, holding a thermometer and note the air temperature. Now step into the sunshine and again, note the air temperature without exposing the thermometer to the direct sunlight. What you'll find is that the air temperature is the same in the shade and in the sun but YOU will feel warmer in the sun. Why? Radiant energy, courtesy of ol' Mr. Sol, 93,000,000 miles away, throwing radiant energy all that distance and it becomes heat when it strike an object, such as your body (or the thermometer if you allowed it to be directly in the sun.

You can find further reference in many posts on this site from pros who will state that taking the temperature of a furnace must be done where there is no radiant effect from the glowing heat exchanger. Those of us who play in the cold country are very familiar with radiant heaters of many different types. Sure, there's radiant slab floors, radiant walls, radiant ceilings, radiant furnaces called infrared furnaces. In fact, old electric strip heaters also put out their fair share of radiant energy, albeit at some higher price.

The fact that your floors are a heavy slab of cold, absent a system to actually warm the floors, you'll feel cool in the room. Thick wall-to-wall carpeting would be one solution to cold floors (that's really where the concept of wall-to-wall began, in homes that leaked like a seive and had cold floors). If you want to install a boiler fueled by your favorite fuel, you could consider putting radiant heat in the ceilings of the affected rooms and they're guaranteed to warm the floors. You see, radiant energy doesn't become warm/heat until it strikes an object. So radiant in the ceiling will travel to the floor before it converts, thus warming the floors. Radiant is another whole science but one that affects both warm and cold climates. Interesting, eh?

[ACFIXR]

Well written skip,thanks for your input. And your right about "feeling cool" in the room. We are so use to absorbing radiant heat here that it is shocking when it radiates the other direction, from you to the floor.
What I am taking away from this experience is that I will now recommend that stuccoed wall system insulation be extended down over the edge of the slab. Especially on elevated slabs with exposed stem walls. In floor duct or radiant floors are not typical in our zone.