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terry j

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Reply with quote  #1 
We have all seen it done, but as wood is a goodish insulation how much of a compromise is it??

I went to my local distributor of PEX pipe (I presume it is) as, if it could be done-well it can be done so-if it could be done effectively then it would save me ripping up the already wood floor in the kitchen.

basically he heavily advised against it due to the 'insulative qualities of wood'.

I had assumed he would also be able to supply the formed aluminium spreaders (which I would prefer to not have to make but can) which is how the subject came up. Natch he does not as he did not think it a good idea.

As I only have about 18 inches under the floor in which to do a 'massive' job like that I'd rather not take a punt if it is not a good idea.

I mean I get that POV, but the heat HAS to go somewhere right? So surely as long as I insulate it well under the stapled up pipes the heat has little option but to warm the wood and hence the room? And being a kitchen there will not be underlay and carpet above it which would 'worsen' the situation.

Yes, having it in a slab is optimum, but is it THAT much of a better option it is worth ripping up a perfectly serviceable existing floor and all the joists and bearers and laying a concrete slab.

That does not compute to me, so what is the real answer here? Does anyone know?

On a sidenote, someone on this forum has used the term 'limecrete' a few times. I forget who, but that rings my bells just a little. The house here (in Australia) was built in the 1830's. This might be 'funny' to some of the readers in other countries, but here in Aus a house built in the 1830s is OLD man!

Anyways, leaving aside the thought that a house built in the 1830s is OLD is funny to a guy living in england where buildings go back to the 1400s the house was built with lime mortar and render etc. So all of my renos I have also done in lime. I do NOT want bloody concrete/cement anywhere near the place. The amount oif concrete I have had to remove from dodgy repairs still gives me nightmares.

We will be extending sometime soon, and I will have to get council approval to NOT lay a concrete slab! (it just forces the moisture into the existing walls and destroys them as concrete does not breathe)

The firm I buy all my lime putty from has never even heard of the term 'limecrete' (which I gather is if not common at least known in england for example).

So, if you read this I'd love to get more data if possible on 'limecrete'.

SolarInterested

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Reply with quote  #2 
Quote:
Originally Posted by terry j
... the heat HAS to go somewhere right? So surely as long as I insulate it well under the stapled up pipes the heat has little option but to warm the wood and hence the room? And being a kitchen there will not be underlay and carpet above it which would 'worsen' the situation.

No direct experience with this but what you've said is what I've always thought too. Having it under the floor may just result in some more lag time until the room warms up.

Gary's BuildItSolar site has some alternatives:

http://www.builditsolar.com/Projects/SpaceHeating/Space_Heating.htm#Distribution

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Garage_Hermit

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Reply with quote  #3 
Hi, Terry,

there is always the option of using a radiant wall (or even a radiant ceiling).

I seem to remember reading that a radiant wall really needs to be fifty percent of the floor area of the room, to be any good, no idea if that is true or not...

I might be the guilty party that has used the term "limecrete" on here a few times [rolleyes].

It just means "lime concrete", that is, concrete that uses *lime* as the binder, rather than cement.

I am using limecrete in my crawlspace renovation.
This is for several reasons: as I am working by hand (no space for a mixer), it can be mixed in small batches and does not go off as fast as cement concrete. It also accommodates my muck from the earth floor, so I do not have to haul sand and aggregate.
I mix it with pine straw to make an insulated slab, so I believe I have invented the term "pinecrete" !

Finally, a limecrete floor manages moisture better: it stops liquid water rising through the slab, but allows vapor moisture out; a wet floor is a cold floor !

Maybe that firm has not heard of "limecrete" but maybe they have heard of hemp-crete" ? (sometimes called "hemcrete").  https://en.wikipedia.org/wiki/Types_of_concrete

======
Regarding your staple-up idea: I reckon it ought to work under wood, the problem with your site is you do not have nearly enough height to work in, by the sound of it...

My CS is 85 cms high or so, it is too low for some tasks ! and I generally wear a hard-hat in there !

I have electric infloor radiant in the floor-above, and it leaks heat downwards into the CS, even though there is 2 inch of styrene under the conductors.  So you really would need very effective insulation below your staple-up, I'd forget it, honest...

Cheers,

G_H

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terry j

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Reply with quote  #4 
firstly, thanks guys. I was 'hoping' there might be a link to hard data on this, I am often amazed at the variety of links that get posted, but as yet nothing harder than gut feel it seems. tho, as said, it has been often done so there has gotta be some fire to that smoke.

You're probably right GH, there is so little headroom it simply might not be feasible, and I have my doubts how flexible PEX would be, it would be a major PITA to get it done. I have seen some pics how you loop the pex thru the joists and let them hang before stapling up, well I simply cannot do that. (hmm, seem to be using simply a lot, maybe the forum title is impinging on my subconscious heh heh)

Wall radiant is not an option, the walls have gotta be at least a foot and a half solid brick (what a lot of heat loss thru that eh?) and hard plastered. Lime of course! So you da limecrete guy eh? thanks for responding to that. Yep, concrete/cement does not breathe and lime does. It's ok if you design and build for each, but you get major trouble when you use cement products in a lime building. The trouble is, the problem these tradies (usually) were trying to solve involved moisture, and being modern well they had no idea about traditional building methods (lime) so using cement just worsens what they were trying to solve! The damage caused just has to be seen to be believed. Thanks for the link, will check it out. I am probably over thinking it, and should just use sand and lime and be done with it. just gotta get that thru council.

Even if I don't end up stapling pex under the floor, I should at least fix insulation under it. That has got to help heat loss even if only slightly.

Anyway, hopefully a link will turn up with some hard data on this question.
terry j

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Reply with quote  #5 
well, I'm convinced that I met a guy who was not up to date with his trade. browsing thru the links given by solar interested there is plenty of 'evidence' (but no hard proof) that it is viable, as we all suspected. Would have thought somewhere out there on the net this has been studied and quantified. But if it works, I spose that is the main question answered.

To wit http://www.radiantec.com/pdf/Within_Joists_Installation_Radiant_Heat.pdf and (much more comprehensive-have yet to study it) http://www.radiantcompany.com/wp-content/uploads/radiantcompanymanual.pdf

What I find intriguing is 'how much work has this guy missed out on by not knowing that an underfloor retrofit is viable'?

talk about cutting your own business throat.

Anyways, thanks for the links, all i have to work out now is whether it is possible in my circumstances to do this.
stmbtwle

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Reply with quote  #6 
Would it be possible to put the PEX on top of the existing floor, and cover it with flooring?
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Willie, Tampa Bay
terry j

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Reply with quote  #7 
hi stumble ([biggrin])

yes, that is always a possibility. kinda 'defeats' the purpose somewhat tho. The initial attraction (given the difficulties of installation) was that I had a 'perfectly useable floor' that did not need removal. And even if I did lay a new floor on top, I am sure I would need to get down in that crawlspace (emphasis on crawl in this case haha) and still insulate it. I think it is worth a try at least to see if I can get the pex in there as well.

BUT, there would be thermal mass etc, and ease (apart from installing insulation) of doingness in your idea.

I could not find it in my quick scan just now, but I mentioned in my initial post that not having carpet would help, but there is a mention of 'wall to wall carpet' in one of those links, meaning that even carpet on top is not too much of a put off. Learning stuff!

Anyways, yes, that is feasible as long as the extra height of the final floor is not a problem, and how the floor levels match up throughout the house.

I'm the type who thinks 'basically anything is doable, it's just that some things are more a pain in the arse than others'. this definitely falls into the PITA category, but equally it (should) be doable.

Kinda excited. what does that say about me??[eek]
stmbtwle

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Reply with quote  #8 
Back off on the coffee?

I agree with you that "some things are more a pain in the arse than others".   That said it's your decision to decide which is preferable.

Suggestions:

Could you prefab your PEX into assemblies complete with insulation that you could slide in between the joists and connect? 

What's the possibility of insulating the sides of the crawlspace and then simply blowing warm air in there via a heat exchanger?  Hot air rises and will heat the floor for you.  Probably not as efficient as a pex setup but it would be a LOT less work to install.  You'd have to ventilate the space in warm weather (there are temperature-sensitive vents for that).

I understand the attraction of a nice warm floor, but if you're willing to give that up there are a lot of other options, baseboard heaters, fan coils, and radiators among them.







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Willie, Tampa Bay
gbwillson

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Reply with quote  #9 
Terry-

One thing often forgotten about wood is that while it has some insulating value, it retains heat quite well. So the mass of wood for the floor and sub-floor, say perhaps, 2" thick, plus the floor joists, gives you a lot of heat retention to last throughout the night if you don't have a warmed water tank built into your system. While I only dabble in solar air heaters, I pump lots of warm air into my basement. And the hardwood floors above are noticeable warmer underfoot. This stored radiant heat helps keep the furnace from firing up during the frigid winter days. On many, if not most winter days my furnace doesn't turn on but twice per day; Once early in the morning, and again after dinner. This is due to the heat I have pumped into the basement. I tried bringing the heated air up from the basement directly, but after some experimenting, I noticed the furnace ran more often when I did.

Greg in MN[wave]
Garage_Hermit

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Reply with quote  #10 
@Willie, good idea about the Crawlspace warm air.

that is called a "conditioned crawlspace"  BUT the air needs to be exhausted back OUTSIDE, all year !

It is also only a very small airflow, like 1 CFM per 50 sft of CS floor.

Best way to control humidity in a CS.  It equates to Option 3 in this link:

http://www.greenbuildingadvisor.com/blogs/dept/building-science/five-ways-deal-crawl-space-air

I am not sure, how much this actually WARMS the CS.
However, even if it does not actually *heat* the CS, it will make for a dryer environment down there, which, I guess, automatically means warmer...

For my CS, I need around 50 CFM of continuous air exhaust to outside, I am looking at this right now, actually.

G_H

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(1)  "Heat goes from hot to cold, there is no directional bias"
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