Temperature of brew compared to room temp

[titeyorkshire]

Hello,
Does anyone know roughly how much higher the brew temperature is than room temperature during the primary fermentation process?
My rooms are all pretty much 15°c. Obviously I will have the starting temperature correct when I mix my warm and cool water and will check before adding the yeast, so it will begin at 18-20°c. I read that the fermentation process creates its own heat, especially at the beginning when it is more vigorous. Will it maintain its own temperature between 18-20°c for the 7-10 days of fermentation in a 15°c room? As you can tell I don't have a heating belt and I don't want to go poking around every day lifting the lid off my bin taking temperature readings...
Not even sure how I will move my keg somewhere cooler to clear later on, as the temperature is pretty steady throughout my whole flat...modern insulated buildings...

 

[Banbeer]

If my memory serves me well the temperature usually rises around 2C so putting your brew at around 17C but that's not all the time it's fermenting. As for a temp reading @Kegthat.com have stick on Thermometers at 60p.

 

[titeyorkshire]

Ok so blanket and stick on thermometer it is... Darn I wanted to make this today. Gotta wait for the postman again...

 

[Clint]

Will your house stay at 15 in this warm weather? The cider I got on the worktop in the kitchen is at 22...no heater or blankets.

 

[kelper]

It will rise about two degrees above room temp but only for the first day or so and then it will start to cool. But, if you wrap it in blankets or similar you can stop it getting cold. It will produce less and less heat as the fermentation slows. But if the weather is warm where you live it should be OK.

 

[titeyorkshire]

Will your house stay at 15 in this warm weather? The cider I got on the worktop in the kitchen is at 22...no heater or blankets.

Its a modern (8ish yr old) flat with loads of insulation and only a tiny bit of direct sunlight comes through the window in the morning and then its gone. The temp today has been steady at around 15/16, even though it has been around 24 outside. We do have the windows open and the french balcony door, otherwise with all that fibreglass crammed in the walls it does get warm and stays warm but we like it cool on a day like this. Might have to get a belt heater thingy. Sounds funny to say with the weather as good as this.

 

[kelper]

I'd suggest a cheap aquarium heater. The belts are hit and miss. I bought an aquarium heater on eBay but wished the stat could be set for 18. its minimum was 20 which might be too warm for some brews as I put it in a water bath. I normally brew in a 25-litre FV which is inside a 35-litre FV with the aquarium heater in the outer vessel so the inner one can remain airtight.

 

[Gerryjo]

I've 2 DJ's wrapped in a sleeping bag inside a shopping bag maintaining around 19° in the garage..

 

[titeyorkshire]

I've 2 DJ's wrapped in a sleeping bag inside a shopping bag maintaining around 19° in the garage..

Hmmm...sleeping bag. Good point. I've got one kicking around somewhere...