Yeast is very sensitive to temperature. Different strains of yeast have different ideal working temperatures for fermenting beer. You want to follow instructions for your yeast to make conditions optimal to produce a great beer.
Fermenting ale’s generally require a temperature between 68 and 72 degrees Fahrenheit. On the other hand, lager requires a temperature between 45 and 55 degrees Fahrenheit.
Not maintaining the proper temperature for your wort during fermentation can result in off flavors. Many of the off flavors will be produced in the first 3 days of fermentation as that is when the yeast is most active. Not to mention that the process of fermentation will produce heat and will raise the temperate of your wort above the room temperature.
For me, I’m considering making a fermentation chamber. The keezer build went very well and it maintains a chilly 36°F. Way too low for fermentation, but great for serving. The best thing is that I didn’t have to wire anything to make it work. I just bought a chest freezer, made a wood collar to make it taller for kegs, provide a medium for installing the taps, and added a temperature controller that turns the freezer on and off to maintain the temp just 3 degrees above freezing.
This time, I can’t spend $180 of a chest freezer, but would love to convert my old mini fridge into fermentation chamber. Still need to get a temperature controller, but the price on those has come down significantly since I purchased the one for my keezer.