I keep hearing concerns that Radiant Floor Heating can put out heat like baseboard? So, when it is Warmboard v. baseboard….baseboard wins??? Thoughts? Thanks
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That's a comparison that can't be made based on words. What's the btu output of the heat source? What's the water temp? What are room conditions? As a generality, I don't think the premise............holds water. r r r
I agree with CH . I have RFH in a basement and it heats the first floor to with in 10degrees of the basement . Still working on first floor so it is warm enough. The basement is set at 70 degrees.
You can melt snow and ice for roads, driveways and walks using the same equipment so heat output is not the issue.
The two things that control output from a radiant floor are:
1)Surface Temperature based on comfort
2)Heat Transfer Co Efficient based on laws of radiant and convective transfer.
As far as comfort and floor temperature goes here's an illustration from my eBook on comfort.
http://www.healthyheating.com/blog/images/Floor%20temp_01.jpg
For every degree you heat the floors above 84 deg F you will have a corresponding increase in the number of people who will find it uncomfortable. So 84 deg F is the recommended maximum.
As far as output:
The output from a radiant floor is a nominal 2 Btu/hr/sf * deg F difference between the floor temp and the room temp. So a room designed for 70 deg F and limited to 85 deg F floor temp has a capacity of 30 Btu/hr/sf. (85 deg F - 70 deg F) * 2 Btu/hr/sf *deg F = 30 Btu/hr/sf.This tells us that any load greater than 30 Btu/hr/sf is going to need supplemental heat regardless of fluid temperature or tube spacing.
So that is the short and sweet of it.
RBean
http://www.healthyheating.com
http://www.healthyheating.com/blog
Edited 1/23/2005 9:16 pm ET by RB
>This tells us that any load greater than 30 Btu/hr/sfThat's a pretty high load. I'm doing 8 btuh/sf w/ 14° design temp. We usually do twice as good as traditional construction. So 30 would involve some pretty serious losses, no?
So - no problem heating for you.
Your challenge won't be heating but actually enjoying the "warm floors."
At 8 Btu/hr*sf the floor temperature only needs to be:
[8 Btu/hr*sf / 2 Btu/hr*sf*deg F ] + 70 deg F = 74 deg F. floor temp at maximum load.
If you were to take the temperature of your foot it would be a nominal 80 - 84 deg F...So would a floor operating at 74 deg F feel warm or cool to you?
The only way to boost the floor temp so it feels warm is to reduce the heated area of the floor so the load per sq. ft. goes up.
Its possible to do this by looking at traffic, furniture etc...and installing the system in these habitable areas but leave out the uninhabitable areas.
Is this useful information for you?
RBean
http://www.healthyheating.com
http://www.healthyheating.com/blog
I'm a number's wonk, so all of this is fun to read. My own case is kinda complicated, but works really well for me. I get to walk barefoot all winter long, so I'm happy as a pig in mud. But let's not take attention away from the original question...whatcha think of his comment re rfh and radiant baseboard?
Based on my interpretation of the original question...the attached graphic is a fairly accurate representation of how baseboard puts out heat vs radiant...
http://www.healthyheating.com/blog/images/Radiant%20vs%20baseboard.jpg
By the way do you know how one attaches pics...uploads etc...? Have tried the attach file...adjusted my browser cookies - security software...nuttin' will keep trying.
Will try to put up some other stuff dealing with this topic.
RBean
http://www.healthyheating.com
http://www.healthyheating.com/blog
Edited 1/23/2005 11:06 pm ET by RB
I like doing it directly...so people don't have to click nuthin...
View Image
Characterized Heating Curves for different systems
My Norton Pro prevents uploading unless I disable as I have done here...RBean
http://www.healthyheating.com
http://www.healthyheating.com/blog
I like doing it directly...so people don't have to click nuthin...
How, exactly does one do that?Scissors cut paper. Rock breaks scissors. Paper wraps rock.
one way to do it is to right click on the graphic... if it displays a menu , select "copy"...
then paste it into your post... viola (sic ).. how 'bout them Pats ?
View Image
Mike Smith Rhode Island : Design / Build / Repair / Restore
Thanks, Mike.
I tried doing that with Cloud's graphic to see if I could repost it on my post and I didn't get the copy function. View Image
Worked this time.
I don't know about them Pats. We don't get football here. We don't know how to play it. Just basketball. How bout them Cats? Seriously, it's looks like you guys are getting a dynasty going up there. I like the Pat's, but I'm gonna have to root for Eagles in this one. They haven't been there for a long time. Good luck.Scissors cut paper. Rock breaks scissors. Paper wraps rock.
Okay, I liked the "Characterized Heating Curve" from 70F to 10F. But where is the other half of the chart? You know, the part from 10F to -50F? Where you really want to be right. <G>
David Thomas Overlooking Cook Inlet in Kenai, Alaska
yeah, cloud.... where is it ?Mike Smith Rhode Island : Design / Build / Repair / Restore
I had originally posted the graphics and cloud made them come alive - so the challenge with internet communication and being new to the site is not knowing if a leg is being pulled whilst winking or sticking tongue in cheek - or if in fact you really do want the other part of the graphs...or are you giving cloud the
View ImageRBean
http://www.healthyheating.com
http://www.healthyheating.com/blog
Yeah RB, where is it?Mikey pull my leg? Naaaaah.No good deed goes unpunished, huh?!
Ok...then here we go...we'll do our best to throw a wrench into the gears...
The other half - for the further north - don't exist in the literature from which they were taken (tekmar).
Is there a need to extend the graphs? I suppose.
The curves extend with "like" direction after 10 deg F.
The short strokes - characterized "curves" are another way of programing weather compensators (indoor/outdoor controllers) for regulating boiler fluid temperatures rather than using traditional reset ratios(1:1, 1:1.2, etc...) which are "linear". It allows the contractor/homeowner to "customize" the settings based on system "character" rather than play with generic ratio's which don't take into account the type of heating system. ( if that doesn't mean anything to readers that are just dying to know - please advise and I'll do my best to raise the level of confusion ;@)
A sample of a traditional reset ratio (courtesy of tekmar controls).
View Image
RBean
http://www.healthyheating.com
http://www.healthyheating.com/blog
Edited 1/26/2005 12:11 am ET by RB
Edited 1/26/2005 3:22 pm ET by RB
I forgot to put in the "<G>" in my "complaint".Obviously, that chart wasn't for a subarctic climate, it supposed a pretty leaky and only moderately insulated house. Extending those curves for another 60F would give RFH temps of 130-190F, something I don't have to do at -40F. And radiator, fintube, and baseboard temps well over boiling, yet clearly those technologies work fine in Fairbanks if the house is built right.Heck, the chart shows a RFH (low-mass) of 100F for 40F outside temp. Not true in my house. At 20F, my water temp is dialed down to 85F. At 35-40F, I turn off my heating system.David Thomas Overlooking Cook Inlet in Kenai, Alaska
I knew you were kidding.It's that Smith guy we gotta worry about. Hope he's happy now. Ha ha ha!
So will the heat loss freeware will not work for me? I didn't follow which chart is wrong?
It could work for you. My point is that someone not experienced with it may not know all the things to look for. For example, one that I use defaults to Seattle. And the place to change it is not obvious. So a naive user could easily live in Maine and produce a load calculation based on Seattle temps. Other similar traps, too. Know what I mean?
I understand what you are saying. Do you have any experience with the free one listed above?
No, sorry.
Can't use Mike's method with a Mac...gotta use html, as in <img src=address_of_picture>.The graphic I posted was RB's...all I did was make it in-line.
Thanks for the very helpful info. I now understand the first formula. How do I calculate how many btu's I need?????
The house is 2980 sqft 9' ceiling first floor and 8' on second. R19 walls, r38 attic, windows with a u value of less than .34, 35 windows, 2 36" doors and 6' slider. Will this house need more than 30 btu per sqft? Or will I burn my feet to keep up on a -15 day?
Google "hvac load calculation". Add "shareware" in there to see some free-ish software. Your mechanical contractor, or whoever selected heating/cooling components coulda/shoulda provided this for you. I don't necessarily recommend diy on this--it's easy to overlook things like the appropriate design temp, etc.--but it can be fun to play with the numbers and see the effect of things like varying the insulation, or glazing, or wall composition, etc. That's educational.
What is design temp? Thanks
In winter, houses lose heat...they lose more heat as it gets colder. Opposite in summer. So, do you base the heating system of your house on its needs with 32° temps, or 20, or 5, or 0, or what? Because which of these you choose makes a big difference in the size of the heating system.If you examined temperatures where you live for maybe 100 years, you'd be able to graph the low temperatures the region experienced each day. So, perhaps the 95th percentile low temp is 20°, and the 97th percentile is 16°, and the 99th percentile is 10°. Or whatever. Now, you likely won't base your heating system on the absolute worst temp ever experienced there--it'd be a waste of capacity--so you pick some percentile other than 100th. Some people use the 99th percentile. Some use 97th...the temperature that you're likely to exceed less than 3% of the time (or 1% or whatever). That temperature, in your area, is the design temp. There are tables built into the load calc software for most big-ish cities in the US with this data. For me in NC, my 97th percentile is 13 or 14. We based our heating system on supplying the heat lost at that temp. Last night was one of those odd nights when the temp was under 10°, so we lost a bit more heat than we put back into the structure. No big deal, put a sweater on. The alternative would have been to use an 80,000 btu/h heat pump instead of a 50,000 (not my actual numbers; just for illustration), but we made the decision that it wasn't worth the added expense for the few days each year that it would matter.
Thanks alot. This info is great. I am only concerned because I live in up state NY. The temps get low often times for a week or more and when you go 1 week losing more heat than is put out.....the end of the cycle is cold in the house. Forget the sweater bust out the parker!
You can get these heat loss calculator as shareware you said doing a google search.
"I keep hearing concerns that Radiant Floor Heating can put out heat like baseboard? So, when it is Warmboard v. baseboard....baseboard wins??? Thoughts? Thanks"
I do not understand the question. What problem are you trying to solve? Do you have a small room with a lot of heatloss and carpeting? Perhaps RFH would not be able to provide enough output in this circumstance. Perhaps baseboard or radiant walls would be better. If you have enough radiant area with enough heat transfer potential, RFH can do the job.
The advice I received which I am certain is based on a "bad RFH" job was that RFH can't do the job that baseboard does.
Some comments were:
"Base board puts out more heat....just put up with the look.....it is cheaper and easier to install.........who cares the centers of large rooms are cold, at least your whole house is not cold"
The RFH system would be for a new house mostly likely using warmboard or another type of surface mount method.
I did a search of our database and found this text addressing another simlar topic - its not exactly focused on this conversation but it has some good points to consider.
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"I think it’s awesome when individuals take the initiative to learn this stuff but while navigating ones way through a fairly complicated process we should also learn about why the design process even exists. Remember, we don’t condition buildings we condition the people occupying the building so design is more about thermal environmental conditions which a home owner/design builder can easily specify in a contract and subsequently measure for performance for a lot less trials and tribulations than heading down the road of mechanical and electrical design. In our courses we get people to consider a proper HVAC system for a home is going to be equivalent to buying a nice automobile. If the student is the type of person to design and build an automobile of that caliber - then in my books that’s cool – go for it! Then we do a soul searching exercise asking what investment in time and risk are we prepared to exchange for this experience?<!----><!---->
Why? Because for less than $100 and a few hours of ones time, a person can learn all they’ll ever need to write a HVAC Performance Specification which a professional HVAC contractor bidding on the project would have to take responsibility meeting if they wanted the contract. It would include everything from humidity levels, air velocity, heating and cooling requirements, floor temperatures, floor to ceiling temperatures, energy consumption etc… <!---->
The performance specification is what a professional Thermal Environmental Comfort Technician identifies first - they start with the long term physical and psychological needs of the occupants then write an interior environmental specification even before begin the mechanical load calculations begin…so my recommendations to students that want to embark down this path is:<!---->
1. Write a specification of your perfect environment…what it would take to make you healthy, well and comfortable 24/7/365 and for however long you anticipate living in the home…the easiest was to do this is think of all the times you have been uncomfortable and write them down…the list becomes the items you don’t want occurring in your home…cold feet, dry air, drafty, noise, clammy, inadequate domestic water needs, huge gas bills, etc… get the picture?<!---->
2. Then ask your self to bid on your own specification (sounds weird but it forces one to think about taking responsibility for ones own environment)"
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<!---->Here's one example of an HVAC system designed for ones health, wellness and comfort. For a 3000 sf home this would fit into a 15' x 15' area.<!---->RBean
http://www.healthyheating.com
http://www.healthyheating.com/blog
"The advice I received which I am certain is based on a "bad RFH" job was that RFH can't do the job that baseboard does."
True. RFH often 'does the job' better.
Designed properly, either can put out the needed BTUs. The primary advantage to RFH is extra comfort- even, constant heat. Also, RFH operates at lower water temps, which can save energy with some types of heating appliances (condensing, near condensing). Sometimes baseboard is better from a cost/benefit standpoint. Baseboard will often have the edge with carpeting. RFH often has big advantages in spaces with slabs, high ceilings, kitchens, or baths. Sometimes a mix of both makes the most sense. Either way, hydronics is better than scorched air.
Free heatloss software
http://www.slantfin.com/hydronic/index.htmlRBean
http://www.healthyheating.com
http://www.healthyheating.com/blog