Subject: Re: A zero-fossil-fuel studio?

From: [email-masked] (Nick Pine)
Date: 13 Mar 1996 18:00:55 -0500

eteam  <[email-masked]> wrote:

>>... a "Trombe wall" with some dark-colored insulation
>>on the outside and an air gap between the insulation and glazing and some
>>holes to the inside of the house that opened up during the day was a lot more
>>efficient at collecting and keeping solar heat in the house than a plain old
>>"traditional" Trombe wall, with masonry right behind the glass, with no
>>insulation...
 
>This modified Trombe wall sounds interesting however could you clarify the
>constuction as we are still  a bit confused. i.e. is the dark insulation
>exterior or merley outside a wall sandwiched between glass.

The insulation is north of an air gap under the glass.
I guess this was not very clear.

>Put another way,
>does it go : outside / glass / dark insulation / wall / interior ?
                              ^
                              |
              Almost...        air gap
                              
>If so , how does the heat transfer through the dark insulation ?

The sun warms the air in the low-thermal-mass air gap, and the warm air moves
up and through a hole in the top of the insulation and wall into the house,
then back out of the house into the air gap through a hole in the bottom of
the wall and insulation during the day, circulating between the house and the
air gap. At night, a one-way plastic film damper covering the top hole or the
bottom hole or both, closes to prevent reverse air flow and cooling, and the
air gap quickly gets cold and stays cold all night, losing no heat to the
outside world, except what flows through the rest of the insulated wall. The
two holes might be equal sized, each 5% of the wall area, if this operates by
natural convection, or they might have less area if what moves the air is a
fan in series with a cooling thermostat in the air gap and a heating thermostat in the house. 

Nick

PS: The airflow by natural convection is on the order of 

    Q = 16.6  x Av   x  square root ((Tairgap - Thouse) x h)

    cfm    ft^2 of each hole          degrees F      wall height in feet.

---

From: [email-masked] (gcp)
Date: Fri, 15 Mar 1996 20:21:26 GMT

[email-masked] (Nick Pine) wrote:

>And when you mention "successful" direct gain solar mass walls do you mean
>Trombe walls?

>A few years ago, I spent some time explaining to a local architect, a more
>technical person than most, who had taken a few engineering courses on the
>way to architecting, that a "Trombe wall" with some dark-colored insulation
>to the inside of the house that opened up during the day was a lot more
>insulation.

An alternative method is to use transparent insulation material (TIM).
This is a honeycomb structure of transparent polycarbonate, somewhat
like drinking straws at right angles to the wall stuck together  to
form a slab, but stoppered to prevent air convection (sounds like
polar bear fur!).
There is no air flow - heat flow to interior is by conduction - and
temperature control is by external blinds (to stop overheating on
summer days and reduce losses at night).

Construction goes:

low-iron content glass/cavity with motorised blind/TIM/backing sheet
of transparent polycarbonate/cavity (to minimise conduction, closed
horizontally at intervals to minimise air circulation/dense wall with
heat absorbing surface.

This is a bit complex;  however direct solar radiation is not
necessary. It is indicated a well insulated house could have its
entire space heating demand met by a 50m2 TIM wall.

There were several papers presented on this at the
2nd European Conference on Architecture, 4-8 Dec '89, Paris.