Congratulations!!!
What is the brand name of your greenhouse?
Here is one link to a home attached greenhouse.
Go down to 2004 Greenhouse. It will not allow me to direct link to it.
I use electric heaters. Oil filled, milkhouse and a Polonis. My sprinklers come on once a week during winter. So far no problems.
But oil filled do hold the heat and release it later. Whereas when an electric goes off it cools quickly.
This same one can be seen on the florian greenhouse site. It takes longer to down load.
http://www.florianproducts.com/GENEVA_EXAMPLE_PAGE.HTML

Here is a link that might be useful: home attached greenhouse

Thank you. We're very excited and we've literally been planning this for years and building the setup for over a year. Fortunately we have the slab in place w/drainage, water, power and lighting...so much of the difficult tasks are done. I am concerned about the actual attachment to the house and dealing with the siding windows and doors already on the house. Fortunately that side of the house was designed with our greenhouse in mind--so it should all line up. Attaching to the house & slab, siding and sealing are my main concerns...and hopefully the greenhouse itself will go up without too much trouble.

Thank you for the links. They do show some siding details that does help---not to mention getting me more excited to get it going. I purchased the Greenhouse from Charley's and it's their Dover model.

Can I ask if your sprinklers actually spray water directly on to the oil-filled or regular electric heaters? I intend to put in a sprinkler and misting system so the oil-filled models sound good, although I'm not sure I've seen models designed for a wet environment. We're hoping the home-attachment will add insulation to the greenhouse's north side....that and the fact that we can actually open house windows and doors to help heat the greenhouse if necessary. I guess we'll see. We're fairly new to this so I suspect the first year will be a learning experience.

Are there any heaters that can get wet (i.e. hit by sprinkler water) or do you have to sheild them in some way?

Mine get wet but not sprayed directly into the element.
The water does hit all around the heaters.
The oil filled is much safer no element to get wet. And the Polonis ceramic one has a very fine mesh screen and the element is behind the fan. The milkhouse heater does not get wet too much.
Polonis heater.
{{gwi:293159}}

Thanks I'll have to check out the oil-filled heaters and see if there are any models with the controls protected/water-proof.

I was hoping to find an oil-filled electric heater with water-proof controls....but so far no luck. Anyone ever seen such a thing?

I believe you should use a sealer between the bottom sill of the GH and the foundation. The 3- 1/2" wide foam that comes on rolls for use under 2 x 4 sills in new construction would work as well for a GH. Then, if you run a bead of 100% silicone along the edge of the sill inside and out, you should never have an issue with cold air intrusion.

How you will attach the sill to the foundation will depend somewhat on how it's made, but it's one place for which stainless steel is not a luxury, regardless if the fasteners are simple screws or large hex's- most especially if the GH frame is aluminum.

But regarding heat, and the best time to think about it really is now, before you start erecting the GH.... Could you give up a few inches of ceiling height, by raising your floor a bit?

If so, then you might want to look into floor heating cables. Warm floors invariably translate into warm air, especially if you add some ceiling fans, which are cheap to buy and operate and can make a nice difference in heating costs as well as much better summer cooling and of course, the continual air circulation so vital for plant development.

Depending on the temps you want to maintain in winter, you still might need an additional heat source, but not much. BTW: It's easy to waterproof the controls on oil filled heaters. Set the temp, then slip a small baggie over the controls and hold it on with a rubber band.

Good info...thank you...although the raised lfoor is probably out for my purposes.