[Strawbale] PEX tubing in floors

[Rene Dalmeijer]

Shody,

Judging by your questions and responces to suggestions. I suggest you 
get hold of a good book on radiant (floor) heating and low temperature 
heating in general. This will give you some insight into the essential 
workings of low temperature heating. I don't have a specific book in 
mind as all the books I know about are very specific works focussed to 
work according to local codes. (that are not specifically supportive of 
efficient low temperature heating systems)

Barring the above I would say that depending on your location (I expect 
an arid climate) Your heating system can be quite simple you wan't need 
much to keep your SB house warm. Basically what this means is heat the 
areas of floor that you will occupy for longer periods of time like a 
lounge, kitchen, etc. and for comfort the bathroom. I prefer cool 
bedrooms so I wouldn't heat them althoughI would put in PEX loops while 
at it anyway just count on pinching these loops right down to almost 
off.

When you place the tubing count on using loops with runs of about 150' 
depending on your floorspace this would mean about 3-5 loops in total 
for a 3 bedroom house. Make sure the tubing is spaced by about 6-8" and 
not to deep below the surface no more then 1.05 " and no less then 
0.75" . Further separate runs of radiant tubing by at least 10" from 
hot and cold water runs preferably not in the slab at all. (this is to 
avoid Legionairs)

In most cases the most efficient heat source is a heatpump but it is 
expensive and as Tom remarked could be seen as overkill. The problem 
with solar panels is that when you need them most, for radiant heating, 
they have the least output. A bonus of using a heatpump is that you can 
also use it to cool in the summer, in many cases a must to keep the 
heat source primed for the next heating season. Early heatpump projects 
in Europe failed because the underground heat source was drained after 
a few years of only heating. Summer cooling restocks the heatsource.

The combination radiant heating and heatpumps specifically in well 
insulated buildings is a natural.  Heatpump efficiency increases as the 
required output temperature decreases. Radiant floor heating works best 
with low temperatures which is made possible with a highly insulated 
envelope. In cooler places ERV systems become essential to minimise 
heat loss for ventilation needs.

Solar panels to supply summer hot water is definitly a good idea. In 
most cases the temperatures are high enough to avoid Legionairs and the 
system can be kept simple because you don't have to take care of winter 
de-icing.



Rene
On May 1, 2007, at 17:58, strawbale-request at listserv.repp.org wrote:

> Message: 4
> Date: Mon, 30 Apr 2007 15:50:40 -0700 (PDT)
> From: Shody Ryon <qi4u at yahoo.com>
> Subject: Re: [Strawbale] PEX tubing in floors
> To: strawbale at listserv.repp.org
> Message-ID: <682762.72927.qm at web90605.mail.mud.yahoo.com>
> Content-Type: text/plain; charset=iso-8859-1
>
> I see, so a deicing loop would only be needed on a
> evac tube collector because of its insulation and
> shape, flat plate (closed loop) will deice itself.
These remarks prompted me to my above mail as they are, according to my 
knowledge, exactly the opposite of what I understand is correct.

> ...I gess the other problem with radiators filled with
> cold water to cool the air would be humidification of
> the cooled air? This is a little confusing; if the air
> temperture is lowered without dehumidification, would
> the air become more humid than leaving it the same
> temperature? If the relitive humidity increases, for
> the comfort of humans, should dehumidifcation also
> take place, hense the popularity of regular A/C
> because it does both?
This is quite correct by lowering the air temperature you increase the 
relative air humidty content (relative to condensation temperature for 
the moisture content present in the air) ie you bring it closer too or 
even exceed condensation temperature. Conventional A/C systems deep 
cool air ( much lower then the required room air temperature) forcing 
it too condense thus significantly lowering the relative humidity so 
much so that many systems incorporate humidifiers to increase rel 
humidity levels back to normal.

> Shody
>
> --- activism98201 at verizon.net wrote: