Your trees will be happier if you can make sure the roots stay at least 55 degrees or more. If the tree roots are below 55 and the leaf canopy heats up from too much sun from the windows, you could run into some issues. I keep my trees near southwest facing windows but I keep my thermostat set to 65. You can start off with your temps low but keep an eye on the temp of your roots.

The most important issue will be your soil mix. When overwintering citrus for months at a time it is very important your mix dries out evenly and quickly. You can search the forums here for gritty mix or 511 mix. They are both very good for citrus in the north. I'm just now moving my citrus outside, its a process and a bit of a chore doing it every year, but I think it's worthwhile :)

Kristopher

Kris has teh right idea about mixes that dry out evenly and quickly..That would help..

If you should use a bagged mix you could either amend it with perlite or use it from the bag but use a pot only a size or two bigger than the root ball..

Also, I wish I had that set-up...If I could keep my trees cooler than I do all winter in a south facing exposure, I would...I keep mine under 55 so they will not drop leaves nor attract bugs..
The winter sun is not enough to cause defolitaion at those temps,,If you added light, thenyes, keep the roots warmer than 55 degrees..

I would also invest in a good floor or ceiling fan just to keep the air moving about your trees..It discourages bugs and allows you to use humidity in any way you choose fit without having issues...
For me a fan is a must....

Are you going to fertilize them?
Where will you keep them all summer?
What kind of pots?
How will you acclimate them to come indoors?
Do you know how to inspect for bugs before they come in?
Do you know how to find them in winter, not that is will be needed if kept that cool.
Do you know how to prevent pests during the time they are outside?

if you need help, where are here for you..
They are a lot of fun to grow, if the weather cooperates, at least for me..

Mike