Wood is a good insulator so putting heating cord under the shelf will render it ineffective in heating the main enclosure.
You could turn that size enclosure into three Simmie cages. If you intend to go for naturalistic furnishings then splitting it into two would be good. Alternatively, if you are thinking about an arboreal species in the future, set it up as one enclosure, with provision for all the fittings for an arboreal species.
There is not a standard answer to your question because temperatures inside an enclosure depend on both type & strength of heat supply and also on things like size and shape of enclosure, position and size of vents & gaps, construction materials and thickness, external temperatures etc. The bottom line is that most enclosures, especially a one-off design, will involve a certain amount of fiddling with heating devices to get the temps where you want them.
As an educated guess, a 15W heat cord under a tile inside the enclosure, usually a back corner, should be sufficient for your needs. There are different ways you can set it up. My preferred method is given below…
[FONT="]An effective and efficient home-made heat cord “mat”[/FONT]
A 15 W heat cord, a ceramic or slate tile and a thin sheet of MDF particle board can utilised to produce an adjustable heat mat around 25cm2. If correctly set up, this heating method does not even require a thermostat.
The MDF is used as the base. Cut out a piece the same size as the tile to be used. Then, using a cross-cut saw or router, cut a series of channels into the wood, both length-ways and at right angles across it. The channels should be about every 2.5 cm apart and just large enough to press the heat cord into with a little room to spare.
The heat cord is placed into the channels in an arrangement of loops. NO loop should be closer than 5 cm to the next. Place the covering tile on top and allow the heat cord to run for at 2 to 3 days. Measure the air temperature about 5 mm above the centre of the tile and adjust the amount of heat cord under the tile accordingly. Allow sufficient time for the new temperature to stabilise and repeat. Continue to adjust the amount of cord threaded under the tile until the desired temperature is achieved and stable.
The heat cord can be fed in and out of the cage through a couple of small holes in the bottom edge or base. Depending on how much is used under the tile, the rest will simply hang out the back of the cage, where the heat can dissipate into the air. The MDF board can be coated with 4 coats of polyurethane, or similar resin, to make it water proof.
The tiles are heavy and not readily displaced, depending on the inhabitants. However, if you were to find this a problem, a dab of Blu-tack in each corner will hold it in place. The tile can also be held in place by thin wooden edging strips tacked to the MDF base.
I advocate using a tile for a number of reasons. They a fairly good conductors and this allows the heat to spread evenly throughout the tile. This means you don’t get hot spots developing around the cord, the surface temperature of the tile is even all over and the tile will continue conducting heat to a “cold” cold reptile on it, regardless of its position or change therein. Tiles are water proof and easily cleaned and sterilised.
Ceramic and slate come in a vast array of colours and surface finishes. You should be able to choose one that looks good in the given enclosure.
The size and shape of the “mat” can be altered by using more than one tile and/or cutting the tiles in half and rearranging into the desired shape. Cutting the MDF base out as one piece will provide the stability to hold cut tiles together.
Blue
