Report Back from Heatspring Webinar...

[AC_Hacker]

Originally Posted by Mikesolar

Maybe he will yet....

I am a patient man...

-AC

[AC_Hacker]

While we wait...

Here is a slide from the Duluth presentation (also Heatspring), that is an amazingly clever way to do radiant heating:

This has many of the advantages of easily-constructed floor heating, but the radiating surfaces are in front of R-5 (.75" x R-6.7 poly iso), which assures that a higher percentage of the heat energy will be driven in the desired direction. I had wanted to do something like this for my back room floor, but finding an insulating material that could withstand floor-loading, and be 3/4" thick (much less being foil-faced) was a monstrous task.

This plan pictured above uses 3/4" board, which will assure that the aluminum heat spreaders will not 'bottom out' and conduct heat in the wrong direction.

Of course, 1" foil-faced insulation would work just fine, and is easily found as foil-faced poly-iso.

However... I did a search for 3/4" foil-faced foam and located THIS_STUFF, which is a poly-iso with fiberglass reinforcing in the poly-iso core, and faced, two sides with foil.

It is interesting also that it's compressive strength is 25 psi. I used some Dow Formular 150 (15 psi) in my kitchen walls, which seems really dense to me... it seemed almost good enough for floor loading, especially when the load is distributed by the floor covering.

So, 25 psi seems really intriguing.

I was also looking at a similar Firestone product with 20 psi compression. However the Firestone product did have a note which read:

For requirements greater than 20 PSI, phone Firestone’s Estimating Services Department at 800-428-4442

Could open very interesting possibilities.

-AC

[stevehull]

This is very interesting. In our Oklahoma location, the use of radiant floors is a problem due to the rapid change in winter air temps. One day the high is 5 F and two days later the highs are in the 50s. With a typical 3-4 inch thick concrete floor, with inlet water at 75 F or so, you still can have an overheated house with a radiant (or sometimes called "conditioned") floor.

But the walls would not have any such thermal momentum - or at least a lot less.

But how to you attach the aluminum spreaders to the inside of the drywall board? Maybe you don't?



Steve

[AC_Hacker]

Originally Posted by stevehull

But how to you attach the aluminum spreaders to the inside of the drywall board? Maybe you don't?

That is a very good question, that had not occurred to me.

If the plates were glued to the drywall, it would certainly improve conduction. Construction adhesive, or some kind of tile mastic seems like it would be a winner.

The only issue I can imagine is unequal thermal expansion.

There was another slide that showed the application of glue with a small paint roller, to the backside of the spreader plates.

I don't recall the audio mentioning anything about the fact that glue was being used, or what kind of glue it was.

If you actually use this technique, be sure and report back your experience.

This is a two-way street.

-AC

[Mikesolar]

I've done this on a few occasions but not with SM there. The wall was already well insulated and I used strips of 5/8" drywall and put the tubing between them with the plates screwed right through to the stud wall.

The finish sheet of drywall was just laminated on with mud, no screws except a few to hold it in place. I've done it with the normal amount of screws too but you have to be careful. These were usually for bathrooms where there was no room for a radiator, due to stupid architects, haha.

[AC_Hacker]

By the way, I just found another John Siegenthaler Article on much the same topic in Home Power Magazine.

The URL for that article IS_HERE.

Same ideas amplified, better illustrations, if you click on the blue links In "Side This Story", you can get to the images. Similar to the other PDFs I linked to, only better.

-AC

[Ormston]

Had never considdered radiant walls before might just have to try it(as well as floor) in our loft conversion.

We have pipework at 100mm spacing in the ground floor screed, but could only do 200mm spacing on the first floor due to that being the the standard spacing for Myson aluminium heat spreaders.
This has given us the issue of a warm ground floor and not quite warm enough first floor when running very low flow temps (Max 28C).

If I use radiant walls as well as floors in the loft this might just give out enough heat at such low flow temps(ASHP cannot manage any more) and with the space above the first floor heated, that will hopefully reach temp too.

Steve

[AC_Hacker]

Originally Posted by Ormston

Had never considdered radiant walls before might just have to try it(as well as floor) in our loft conversion.

We have pipework at 100mm spacing in the ground floor screed, but could only do 200mm spacing on the first floor due to that being the the standard spacing for Myson aluminium heat spreaders.
This has given us the issue of a warm ground floor and not quite warm enough first floor when running very low flow temps (Max 28C).

If I use radiant walls as well as floors in the loft this might just give out enough heat at such low flow temps(ASHP cannot manage any more) and with the space above the first floor heated, that will hopefully reach temp too.

Steve

You have some really interesting information here, especially for EcoRenovators in the US.

As a basis for understanding, your heat loss is obviously very low. It would be useful to know a bout that.

I would like to make sure that people in the US understand what you are doing.

You have a hydronically heated cement slab on the 1st floor with PEX spaced at 4 inch intervals.

You are also hydronically heating your 2nd floor with PEX spaced at 8 inch intervals. You would like to have the spacings closer, but your aluminum heat spreader(s) will not allow spacing PEX closer than 8 inches.

Your water feed temp to both floors is running at a maximum of 82 degrees F.

As a result of your 2nd floor PEX tubes being spaced at 8 inches, even though you have aluminum spreaders, your above-the-subfloor construction is running less efficiently than the 1st floor.

Ormston, did I get all of that right?

The most remarkable part of your post is that you are successfully heating with a feed temp of only 82 degrees. It would be very useful to know what your indoor air temperature is.

Some other of the things I see that is remarkable is the 4 inch spacing in your slab. I'd be very interested in knowing the thickness of the slab, and what kind of insulation you have under that slab, and what diameter PEX are you using?

I'd also like to know how that slab was laid out to allow you to get 4 inch spacings. I have an inkling how you did it, but I'd like to hear it from you.

Another thing I think is remarkable is that an 8 inch spacing, even with aluminum spreader plates, will not supply heat as well as the slab.

It is a bit like comparing oranges to apples, because of the differences (cement vs built-up with aluminum, PEX spacing, etc.).

What do you think made the difference?

Best,

-AC

[Mikesolar]

In my conversations with fridgies over on that side of the pond, 100mm is ideal and the best for good HP performance. When I did my moms house back in 93, we had typical 12" on a concrete slab and NO heat on the second floor (1st floor to you Brits). I never use 12" anymore in a slab, always max of 8" and 4-6" in gypcrete. Their tubing is 15-16mm OD typically, same as ours.

I'm curious to know what the air temp difference is between main and upper floor is because in my moms house it was only about 2-3C which was much better for sleeping.

[Ormston]

Pipe is 17x2 PEX, that is 17 OD and 2mm wall.
As this is a renovation project things were incomplete when we moved in last November, I manually balanced the flow through each zone and run the system with no thermostats. It was controlled using weather compensation (certain outside temp = certain flow temp).
We generally had 21-22C air temp on the ground floor and 17-18C upstairs, not quite warm enough when getting out the shower.
Attic was poorly insulated as loft conversion was planned.
I think the main issue is that PEX in screed with carpet covering emmits far more heat than PEX with aluminium spreaders through wooden floor boards and carpet covering.

Will post more details and some photos when I get home.

Steve