[Greenbuilding] Hydronic Radiant Underfloor Heating
Gary Viljoen
gary at humanworks.co.za
Mon Oct 15 07:28:32 EDT 2007
Thank you all for the quick response.
To clarify:
By 'polystyrene' I mean compressed foam boards used for insulation. Is that
what you are referring to as 'rigid insulation'?
And does your 'poly' refer to thin plastic waterproof sheeting instead?
So, if I'm correct and working from bottom to top, I start with:
1. Well compacted and level base, then
2. Compressed foam/rigid insulation layer on top (with an additional strip
running along the foundation walls), then
3. Plastic waterproof sheeting on top of this, then
4. Steel mesh positioned at approx 40mm above this waterproofing layer
5. Hydronics piping tied directly onto the mesh, then
6. Concrete surface bed poured over this, then
7. Screed to follow
Please let me know if that sounds right.
Any ideas for a 'greener' product to use for the under-slab insulation
(greener than the compressed foam - polystyrene - insulation)?
Also I would like some input on how to lay the pex piping. What is the
optimum length per square meter? Meandering pipes or tight turns??
Gary
Ps: By the way, life in Cape Town is magnificent this morning!!
-----Original Message-----
From: greenbuilding-bounces at listserv.repp.org
[mailto:greenbuilding-bounces at listserv.repp.org] On Behalf Of Clarke Olsen
Sent: 14 October 2007 03:18 PM
To: jfstraube at uwaterloo.ca
Cc: Greenbuilding at listserv.repp.org
Subject: Re: [Greenbuilding] Hydronic Radiant Underfloor Heating
I would underline that part about compacting the gravel. Making
the base firm and level
will assure that the slab is close to a consistent thickness,
reducing it's need to crack.
I have used 2 layers of 1" foam in the hope of conforming closer
to the base (and to
stagger the joints).
Don't forget to cut (or embed) control joints in the concrete as
soon as you can.
More joints = less cracks. Sealing or covering the curing slab
will make a harder surface.
ClarkeOlsen
Spencertown, NY
On Oct 14, 2007, at 9:36 AM, John Straube wrote:
> Good advice Mr Green, but I would like to add a few details:
> The poly should always be directly under the concrete topping
> otherwise water can and likely will be trapped between the foam and
> the concrete.
> Foil faced insulation only works when facing a gap.Chris Green wrote:
>> Gary Viljoen wrote:
>>> Hi all,
>>> I am about to install an under floor hydronic system into the home I
>>> am
>>> building, and face two options given to me by ‘experts’:
>>>
>>> 1. Lay the concrete surface bed. Place polystyrene insulation on
>>> top.
>>> Lay the piping in the screed above this.
>>> 2. Insulate below the surface bed with the piping in the concrete
>>> surface bed.
>>>
>>> Any recommendations based on experience?
>>>
>> Either way, but the first way just adds extra work and probably uses
>> more concrete.
>>
>> My experience recommends this way:
>>
>> 1: Level and compact the soil/ gravel as best you can. You want to get
>> it quite close to flat so there aren't any big voids underneath the
>> rigid insulation. Also, getting the bed flat as possible cuts down on
>> the amount of concrete you'll need.
>> 2: Place 5 1/2"/ 140mm strips of 25 mm rigid insulation along the
>> inside
>> of the exterior wall footings or foundation to prevent heat flowing
>> from
>> the slab to the foundation and out into the great beyond.
>> 3: lay down the poly and seal the joints and any big rips that might
>> show up in it. A few little ones are okay. The poly can run up the
>> side
>> of the footings a ways. Also tape the poly to any plumbing pipes which
>> stick up above the surface. I also use the tape to seal any open pipe
>> ends and prevent concrete from splashing into them (that can happen
>> when
>> pumping the stuff with a pumper truck...)
>> 4: Place the rigid insulation. On one job we even taped the joints
>> between the insulation, possibly because we didn't put poly down under
>> it...or at least I don't recall doing that...
>> ---if you're using foil covered insulation, the foil faces upwards.
>> 5: place and tie the rebar as per the specifications. The rebar should
>> be between 1 to 1 1/2" or 25 to 40mm above the insulation. There's
>> little plastic risers that will set the rebar at the right height but
>> chunks of broken concrete patio tiles work just as well.
>> 6: lay out and tie the hydronics tubing to the rebar grid.
>> 7: do a walkabout to inspect and adjust everything before the cement
>> crew starts working. Repair any punctures the rebar has made in the
>> poly...
>> 8: pour and screed the concrete.
>>
>> ***If I think some patches of the compacted soil aren't quite up to my
>> standards, I'll ask the rebar guys to throw an extra run or two in,
>> reducing the spacing
>> from 2' to 1'. I had to do that on one job this spring.
>>
>>
>> Cheers,
>>
>> Chris Green.
>>
>>
>>
>>
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>
> --
> Dr John Straube, P.Eng.
> Associate Professor
> Dept of Civil Engineering & School of Architecture
> University of Waterloo
> Waterloo, ON Canada
>
>
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