New Mashtun Temp

[Wings]

Ibought a £6 cheapo coolbox from sainsburys for my mash tun and after geting it all plumbed up today i tested for heat loss, and using about 20l of water at 70c over a 90 min period it lost 5c and it was wrapped up, is this too much? What is the most the temp should move by?

I have allready tried to fill the cavity with expanding foam but im not sure it made it all the way round. I dont know wheather to dril some holes in the outside to try to put some more expanding foam in the parts whih do not seem to be filled, or just bite the bullet and buy a better cooler and start again!

Any advice would be great
Thanks

[sib67]

You'll find that it will retain its heat better when you put your grain in rather than just water.

[clogwog]

You can also do like I do.
I have a piece of yoga mat, cut to fit inside the mashtun on top of the mash, and thus isolating the headspace in the mashtun.
I lose only ½ to 1ºC over a 90 minute mash.

[Wings]

Thanks guys, I'll go ahead and see what happens!!