Seed Chamber too hot?

I built a four story seed chamber, eight feet tall and two by four feet wide, fully insulated with four sets of shop lights for each level. It turns out that my garage is probably almost warm enough to propagate most anything with only a couple of lights on an open shelf. I can get the temperature down to 75 cutting the light in half, raising the lights as high as I can, using two fans and no heat mats. Will this be too warm for propagating things that say they need 60-65 degrees?

Yes, way too warm. The warmer the temps, the more light growing plants need. So cutting the light in 1/2 and raising the lights will result in nothing but leggy plants. I find that after seeds germinate, cooler temps are better and result in stronger, stockier plants, and healthier plants.
Can you remove some of the insulation and/or open at least one side?

I had put doors on the front, so I opened them completely. The fans I put in were the ones they use for computer servers . I built those into the sidewalls but pointed them in the direction to evacuate the heat, figuring that was best, but with the door open, I probably need to reverse them . I used the white 40 watt bulbs with 3000 lumen output and the entire inside is white, except for the seed mats which I can now remove which should be enough light to keep them from getting leggy. I built the chamber from some boltless metal shelving I had left over and I have another set of shelves I can use after they sprout that could lighted with the now excess lights to take care of the legginess problem and obviously would be at lower temperatures. I used a sandwich of masonite and 1.5" rigid insulation for the exterior and a rpg board, rigid insulation and plywood sandwich for the shelves. Everything is bolted together so it can be modified fairly easily.

I put a 10x20 seed tray with soil and a cover in the chamber and have been monitoring the temperature. It is staying between 70 and 75 most of the time. The ambient air temperature is fine, staying in the 60 to 65 degree range. There must be some heat build up inside the tray that cannot be dissipated by the fans. Not much moisture built up on the inside of the cover, probably did not make the soil moist enough. I used a mix of equals parts perlite, vermiculite and peat moss.

I am inclined to just go for it, trying the seeds with higher germinating temperatures first and gradually moving up the scale and down in temperature. I probably made way to big a deal in building the chamber but it was fun building it, not something I had ever done before. I can turn the lights off at the warmest part of the day and heat during the cooler part, which should help with the temperature.

The last few nights have been quite warm for here at this time of they year, though the temperature variation is not very great at any time during the year. I am eager to get started in this new venture but do not want to fry the seeds.

Yes, if you reverse the fans you will pump cooler air in and also force the warmer air out the doors.
Should help lower it somewhat. Once the seeds are up the heat mats are not necesary. As for the moisture build up, you really don't want any for your growing seedlings. Too warm or too cold + lots of humidity is a breeding ground for fungus of the damping off kind. I grow lots of seedlings here with little humidity *after* the seeds germinate as we have little to virtually none most times. Never a problem.
I've been using coir instead of peat now and like it alot better. Wets easier than peat, and no worries of damping off.
Good luck!!

thanks for your help. I will try some coir after this pony bale of peat runs out.

Getting rid of the doors, reversing the fans, taking out half the lights and eliminating the heat mats brought the temps down to 68 at the warmest part of the day. Plus, I have enough stuff left over to build Seed Palace jr.

Well, I took the plunge. Planted 10 of the 132 plug trays. Mostly rudbeckias and marigolds, figuring you can't go wrong with those. I did plant a flat of muhlenbergia rigens. The brugs and other solanaceae need to be soaked so that will have to wait till tomorrow. The African stuff can come after I see how this goes. Temps are holding in the high sixties.

Seed Palace Jr, hahahaha!!
Glad it's working. Good luck with the next batch

About two thirds of the stuff has germinated. The higher temps do not seem have been a problem. Hunnemania, Muhlenbergia rigens. a few others have not shown their faces. I took the lids off a couple that had totally germinated. Watered everything from below which worked out fine. Haven't got the chamomile tea yet or the H2O2 for soaking the brugmansias and the daturas. Tomorrow. I did plant 10 more flats and have room for 12 more flats. Haven't done any of the South Africans or Australians yet. I did get some of the smoke disks along with the seeds, so I have to soak them first. I want to get to transplanting before attempting the more difficult seeds.

Down to just a couple that have not germinated, Inula being the main one. Nice to use easy seeds to start with. First ones of the second batch should be starting to come up. I have taken about half the lids off of the first batch. I will take the rest off tomorrow.

The inula is the only one not up. Checked the T&M site and it said 21 to 60 days. Guess I have a while to wait.