6
SHELL CONSTRUCTION
There are many
different ways to build an
insulated box or shell. My
first oven used foil covered
1 inch Duct Board used in
the air conditioning trade.
Using a sharp knife and a
flat iron you can form up
the shell in any size you
want using commercial
heat seal tape. Set the
angle of the face at about
your latitude plus ten
degrees measured from the
horizon (42 degrees in
Tucson) for the best
average performance all
year. When the shell is
complete another layer of
Duct Board is used to form
a liner. This will yield a
total of two inches of
insulation, with foil on both sides.
Sheet metal trim can be used to finish the shell, but most of the metal used consists of small sheets of
scrap metal. After the openings and corners are trimmed the large areas of the sides are left unprotected.
The duct board has been exposed to the weather for eight years without harm (except for the
woodpeckers); however, it is best to cover the sides completely with metal.
The door is sheet metal, one inch thick encasing duct board and two inches thick at the opening. A
leveling compound of silicone gasket paste was used to form a flat face gasket that is nearly air tight.
The door is attached with a piano hinge and a counter-weight, such that the door forms a shelf when
opened against fixed stops.