# Re: A zero-fossil-fuel studio?

```eteam  <eteam@wirrleac.demon.co.uk> 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.

```

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