My wife and I are building a 3000 sqft log home in southeast NY and are not looking at anything but radiant heat. I am a major DIY'er but will limit myself on this job to late night online research on bulletinboards like this to make sure I make the right choices, and running the pex tube myself following engineered directions to save some labor costs.

I have limited first hand knowledge from an uncle who has been heating his 2000+ sqft mid wisconsin home for the last 15 years. He has gypcrete all around, sets his hot water heater to 110 and raises it to 115 on very cold days.

I read the consistent requirement for heat loss analysis. But while doing this preliminary research (rightfully or wrongfully) I assume with a log homes thermal mass and good insulation where there are not full logs, I can have somewhat equal overall insulating properties as a conventional well insulated home such as my uncles.

I have seen radiant setups which look as if they were designed by NASA and can understand the $40,000 price tags. I have also seen my uncles which is very simple and more than gets the job done. I don't care how fancy my mechanical room looks, I just want a reliable heat system and would rather not afford 40k.

My thinking is this. A local supply house can have Wirsbo design my system, I follow the map of pex layout and I find a local pro to do the hot water heater (preferred) or boiler install.

My questions based on the above:

If boiler systems are the more complex set-ups, even if 3000 sqft is pushing it for 1 polaris type heater, can 2 hot water heaters be a better overall plan as far as simplicity, installation cost, troubleshooting down the road? (although not as impressive to look at)

I will get a heat loss analysis. Having said that, if I choose warmboard for example, would they actually leave spaces if there is an expected low heat loss area of the home? Not to shun the analysis, but I'm willing to bet their design will fill up all their 12" oc grooves completely no matter what the heat loss calculation says? And if their engineering is just for temp changes or water velocity per zone, can't that be adjusted afterwards anyway?

My local warmboard rep told me gypcrete can take 24hrs to heat a room. I know there is a slow response time but did not expect it to be that long. Does warmboard really benefit of quicker response time (when the wife wants to crank it up at night when the baby is sick?)

We want to put in a high heat output fireplace. Will this cause confusion for a high thermal mass system, again making me lean towards warmboard.

My DIY portion will be limited to running pex above the floor in gypcrete or warmboard. I also want to run the hot and cold water main plumbing with pex for log home settling issues. Is there a brand recommended where I can buy the crimping/expanding tool and use it for both jobs?

I appreciate any answers, and I am sure you all know how helpful all your advice is to people who care enough to learn about something they do not do on a daily basis.

hi tim,

As you now already know, a heat loss is the first step. From there,most of your questions can be answered, such as, which method of installation is suitable and fluid temps. Then you can pick an appropiate heat source.
in my opinion, you can get a condensing boiler with correct output and indirect tank to simplify piping in the mechanical room,instead of polaris water heater.
Yes,it can take some time for concrete to come up to temp.Floor sensors best in that situation.
Fireplace should not be an issue,zone that room seperate from other zones.
I favor wirsbo tubing for both radiant and plumbing.
N&S in fishkill can help you with design and purchasing tools for pex connections.
Or, email me with questions I am close by.

[This message has been edited by singh (edited 02-27-2005).]

Before you make the decision to use a single source water heater as the heat source I would suggest you consider the potential ehalth impacts of your decision on you and your family. Legionella is KNOWN to flourish under the conditions you are describing. Do you really want to expose yourself and your family to this potentially deadly disease?

The money you save upfront could be more than consumed in the loss of health in the long run...

I used to have a system like this in my own home. I opened the lines after about three years to see whats going on. There was a bluish green slime growing inside of the pipes. When I saw that, I decided that I didn't want to expose my family OR my customers to that possibility. And at that time, I didn't even know what Legionella Pneumonphila was!

Think about it. You're doing the right thing by going with an engineered system as opposed to the Inet "you don't need no stinkin' licensed contractor" route. Make sure you do it right all the way. And I'd recommend that your uncle install a flat plate heat exchanger to eliminate his exposure too.

Mark Eatherton
Licensed Master Plumber/Hydronic Heating Technician.

Gypcrete responds a little slower than a joist space system but nothing like 4" of concrete. A good controler will make it very cosistent and comfortable and as a bonus you get the sound deadening and fire resistance of gypcrete. either a dedicated water heater or my choice a condensing boiler like the munchkin...Eric

Some points for you to think about or suggestions:

1. What are you going to do about cooling? The house will have greater resale value and this will be less expensive in the long run if you factor this now, not later.

2. You should use a boiler and the domestic hot water will be priority over heating. In order to shorten time off the system and give more water as well as backup, I would suggest a tankless on the output of your hot water maker. It is easy to hook up and will only cost about $1K extra.

3. You might consider an outdoor thermostat in order to keep heat on when you use the fireplace. Activating the fireplace will then have no effect on the radiant, unless outside temps rise simultaneously.

4. Direct vent only for the fireplace or tankless or boiler.

5. Do you need an HRV if the house is expecially tight?

Good luck.

Thank you everyone

warmboard is filled at 12" o.c. no matter what. The heatloss tells you *where* to break for additional zones, whether or not hardwood floors will have problems, whether or not you need supplemental heat, what kind of water temps you need and load you have (and thus, partially, what kind of heat source is best).

------------------
Northeast Radiant Technology, LLC
-=RFH Design, Supply and Consultation=-
RPA certified Radiant Designer
http://www.NRTradiant.com
rob@NRTradiant.com

Tim- You have mentioned yet another couple of reasons why low thermal mass is important for comfort. Slabs of any type have significant thermal mass which has the effect of delaying upward or downward response to changing loads by hours or days depending on the amount of mass, the temperature of the supply water, the temperature increase or decrease required, etc.

A typical traditional wood burning fireplace puts out 10,000-15,000 BTUH. If a high mass slab system is supplying just the right amount of heat, lighting a fire in your fireplace for ambience can quickly cause your room to over heat.

With high mass slabs, raising the thermostat setting in a sick child’s room will not affect that room temperature for hours even though your child wants that comfort sooner rather than later.

If you decide to throw a cocktail party, twenty people standing and walking around generates about 10,000 BTUH in addition to the heat supplied by the slab. and can quickly cause you to open windows even in the winter.

One 100W light bulb by itself produces 341 BTUH. A family of four coming home from work or school and turning on a bunch of lights can cause temperatures to over shoot just from the incandescent lighting and the warm bodies.

None of these problems, inherent to high thermal mass, are mitigated by outdoor reset which only measures and adjusts for outside air temperature changes. And a secondary benefit of low mass systems is that because they are easier to control, their control systems need not resemble a NASA job.

Thirty years ago virtually all radiant was done in high mass slabs, and using a computer required stacks of punch cards. Just as we have developed computers that are far more user friendly, the whole revolution in low mass, fast response aluminum based systems such as Warmboard has made radiant floor systems far more user friendly.

It is inherent to comfort that you get the right amount of heat right when you want it.

I think Terry, in is exuberance for low mass systems, is overstating the lag time of a high mass system. I have lived in several high mass houses with gypsum underlayment over radiant tubing and concrete heated floors. It does not take "hours" for room temperature to come up in a sick child's room or any other room unless the system is poorly designed.

There is a basic misunderstanding here. A forced air system could be considered a fast recovery system, but only if one uses air temperature as the sole guage of performance. When a room is cool, all the mass in that room is also cool. Turn up the thermostat and blow a lot of hot air in the room and the air temperature will rise. The mass, such as walls, floors, furniture, etc. has to absorb that heat. The surface temperatures rise slowly. That is why you can turn up the forced air heat in a cold room and, even though the air temperature is raised, the room can still feel chilly for a long time. You are still feeling the chill from the cool surfaces.

A low mass system will bring the floor surface up to temperature faster than a high mass system, but the other surfaces in the room must also be raised to achieve the comfort level set by the thermostat.

It has often been argued that forced air is far quicker at recovery than radiant heating. But that difference shrinks when one considers "Operative Temperature" or the combination of conductive, convective and radiative heat transfer of all the factors that have an impact in the room.

This is also true when comparing high mass verses low mass radiant floors. While high mass systems are slower to respond than low mass systems , the difference is often greatly overstated.