Uninsulated radiant floor

Martin Romero

Many thanks for the feedback on my issue. You've inspired me to do more research.

The house is about 1600 sq. ft. with four heating zones. I'm unsure about tubing length, but I can get more information on the square footage of each zone.

I would consider it impossible to try and install further insulation under the slab, but I could see installing additional insulation at the perimeter, which now has 1" up to frostline.

The boiler is a 90,000 BTU input and is produced by Raypak. I'll see if I can find out just how much propane has been used over the years. My sister is heavy into saving every receipt, so it may not be too difficult.

I'll also call for my propane company to check for leaks. I intended to do this months ago, but blew it off not really thinking it could be a serious issue.

The solar installer I've spoken to gave me an estimate of $10,500 for the installation of 3 - 3x8 Sun Earth Collectors and an 80 gallon heat exchanger tank as well as a "Carlson" 2.0 heat exchanger.

I'm grateful for your input and help and am eager to continue this thread.


Sincerely,

Mart

Martin Romero

Uninsulated Radiant Floor

The house I'm living in is about 7 years old. A slab-on-grade radiant floor system was installed without insulation underneath the tubing (I observed the installation) and the foundation insulation is 1" foam. The house is located near Albuquerque, NM.

According to my sister - from whom I bought the house - the heating system drinks enormous quantities of propane. I'm considering installing solar hot water support for the system, but I'm hesitant.

Can someone out there share some insight.


many thanks,

Mart

kpc_7

thats too bad...

what is the possibility of breaking up some of the floor...can you tell us some more about tye house? size? water temps? what type of boiler/ heat source? what are the tube lengths for the circuts? Anny Pictures would be great! kpc

hot_rod

how much house and how much LP?

So it does have perimeter insulation, down to frost level or footings? How did the house get heated for the last 7 years?

It takes a lot of panel area and insulated storage to do much solar radiant. you might spend the money on re-insulating somehow to lower the heating load. 15- 20 Grand may get you 20- 30% of the load with solar.

Do you have a load calc for the home? Be interesting to see how the actual consumption compares to the load calcs.

Often times it's the cost of LP, not the actual consumption that you are looking at. In my area it has doubled in cost in less then five years. Currently at $2.09 per gallon.

hot rod

Weezbo

not every home is built with the same philosophy or ...

definition of comfort.

This is even true within individual communities and areas of a state . i would go so far as to say that it is even true within any given neighborhood.

Some well intentioned contractors are swayed by the dirt workers or some trade that has little or no understanding of anything other than their own trade ,much less how the combination of efforts produce the quality home. It can be even worse when the homeowner decides to take on or take over the responsibility of the general contractor...by micro engineering things. they have no CLUE what their meddling does to under mind the construction processes and procedures ,costs of construction and future operation of the home.

Even good contractors need to guide some of the quality control on the job of other trades, especially, when they can see clearly that something is far from optimal.

ok then well what does that have to do with you?

lets go another direction around, i have been to New Mexico a number of times. so i wonder about a number of things just reading what little we have to guide us in our answers as to how to best help you. honestly , there are more questions than answers that occur to me.

There are a number of ways and means to any solution. in your case , quickest basic drop that you could get on the Equation would be to get someone who would outline a plan of specific aspects to examine ,compile them and give you an honest appraisal of what you have or do not have.

while we can certainly look at a picture of the heating system or energy recovery system and make some profound changes with very simple solutions at times...it is only a fraction of the over all picture.

Someone on site often realizes what he is looking at, dials in a few investigative tools and bang! remedy ... done deal. some soapy water reveals a continuous leak, for an example, in the gas line near the regulator ...

there are many causes for fuel consumption ....based on fuel costs though may or may not be indicative or even a clue as to "Whats Really going on?" *~/:)

Some radiant floor systems do not have insulation under the tubing, although ...later it is installed under the floor....
many builders have a draft of a wall section, that is stapled to a set of prints ..it may be that information in that assembly has certain vagaries...it may not be remotely like the picture for an example.

Did some work the other day where the contractor put 2" of foam around the plate under the slab on the exterior walls for an example...well,...that type of detail we would all like to see more often as it makes a huge difference in perimeter heat loss. yet, you had no idea that three of the four walls were 1/2 glass until i told you nor would you have divined that it was a gypcrete pour...:)or three stories with a slog.

really the best thing is hire someone to get things together for you see if you can find an advertisement that says something like GSHP, A-C, Hvac, Radiant heating, Solar DHW Energy Star rated building ,Leed's builder and ask one of them for two choices of building inspectors in your area...someone who does Blower door testing would likely have decent information or may even be a building inspector...

well, think about it......you got time.

cattledog

Martin--

I think that a detailed heat loss analysis would be of great help to you. Yes, check for a propane leak, and it would be prudent to verify that most the the energy from the burning propane is going into your water and not up the stack.

But, lets assume that you don't have a propane leak and your boiler is operating efficiently, then you need to understand the whole house heat loss in some detail. This will tell you where to spend your insulation dollars. Given most soil conditions, the periphery of the slab is usually a more significant loss than underneath and it may only be 10% or 15% of the total heat loss. You need to compare this to your ceiling, walls, windows, doors, infiltration rates, etc.

Adding supplemental heating capacity through $10K of solar collection may not be the most cost effective way to cut your space heating propane bill. However, if your domestic hot water is either from an indirect unit or a propane water heater, than you may be in a different situation. Otherwise, managing passive gain and adding insulation may be the way to go. Only a specific and detailed analysis of your house can guide you in what to do.

Martin Romero

Uninsulated radiant floor

Cattledog,

I do have two propane water heaters that could be served by the solar system.

Unfortunately, the house is not oriented very well to allow for passive solar gain. It is long from north to south and narrow east to west.

I'll try out the heat-loss-calculation aid on this site as a first step looking at the house efficiency.


Sincerely,

Mart