Emergency! Garden window question - what glass?

[Pathwalker]

My husband was just forced to tell me what my surprise present is for my birthday - a HUGE garden window! BUT, I need to answer him regarding what type of glass is needed for growing seeds, etc. in early spring in Michigan. My choices are regular glass or "Low-E" glass, and I have no idea which type of glass is best.
So, I'm appealing to all you wonderful gardening experts - which type of glass do I need? And, I need a definitive answer ASAP, as they are waiting on this to order it at the store. My husband is very sad that he had to spoil the surprise, as he loves surprising me on my birthday. Is he wonderful - or what?

Thanks in adavance!
NB

[GardeningGal]

1. I have no idea, but

you might want to cross post in the environment/energy group and see what analysis they come up with.

[Kolesar]

2. Look for a low-e glass window with "high solar gain"

You will want the windows with the highest solar heat gain coefficient/SHGC of all the products available. This web page can explain what it all means.

http://www.efficientwindows.org/lowe.cfm

Window Technologies: Low-E Coatings
Low-emittance (Low-E) coating are microscopically thin, virtually invisible, metal or metallic oxide layers deposited on a window or skylight glazing surface primarily to reduce the U-factor by suppressing radiative heat flow. The principal mechanism of heat transfer in multilayer glazing is thermal radiation from a warm pane of glass to a cooler pane. Coating a glass surface with a low-emittance material and facing that coating into the gap between the glass layers blocks a significant amount of this radiant heat transfer, thus lowering the total heat flow through the window. Low-E coatings are transparent to visible light. Different types of Low-E coatings have been designed to allow for high solar gain, moderate solar gain, or low solar gain.
...more...

Is this a south window?

[TygrBright]

3. Depends on the exposure.

If it's a north or east window you want the regular glass to maximize solar gain. South or west, you're better off with low-E, as summer sun could scorch hell out of your plants.

technically,
Bright

[Pathwalker]

4. Update: After speaking with several commercial

greenhouses in my area, I decided against the Low-E glass, because they all agreed that to get seeds to germinate here in mid-Michigan in March and early April, the Low-E glass does not allow in enough light, and they all recommended regular glass. They all also suggested using either solar film in the summer, or purchase shade cloth fit to the window's size for the summer months, since this is a south facing window 4' X 6'5''. This is the type of glass they ALL use, so I decided to go with that.

I would like to thank you all for your help, and I would also like to share a WONDERFUL money saving tip from my local County Extention Officer: Instead of purchasing those costly seedling heating mats($30-$40), buy a USED waterbed heater mat with Thermostat($5), and wrap it in a sheet. They work even better, she said!!!

:hi: