Temperature Readings In The Cold

So I'm still pretty new to brewing and Saturday I brewed my first below freezing batch, fifth overall. I have an all grain set up in my uninsulated garage and every time I took a temperature reading the temperature seemed to drop 5 - 10 degrees. I have a space heater I use to heat the space, but it didn't get above 40 for the five hours I was out there. I use 10 gallon Rubbermaid coolers for the MLT and HLT and having the top off for the ten seconds the lab thermometer took to get a reading seemed reckless. I let the mash set for the entire hour after taking the initial reading so not to lose the heat and I reached my target OG so I can't complain too much though it may have been more luck than anything.

I guess my question is does anyone have a good solution to compensate for such temperature loss, or should I just break down and insulate the area I brew in? I refuse to wait until spring to brew my next batch so any advice is greatly appreciated.

You can run off some of the wort part way through the mash, heat it and dump it back into the mash to raise the temp. I think most if not all the brewing software should be able to calculate how much liquid heated to what temperature will give you what increase.

I us Beertools and it will tell me that stuff. I use it sometimes when I do something stupid and miss my mash in temp by a bunch.