Can you have too much loft insulation

Question

With the winter not too far away now and the ever rising cost of energy im thinking of maybe adding more insulation in my loft but is this a false economy. I already have whatever is required as the minimum reccommendation but will adding more be effective.

Answer 1

By all means add more but, Do not let it block air movement from the cavitiy walls,More is good,It will cut your heating bills down.

Answer 2

The interesting question is how much extra energy is saved in upgrading from 6" to 8" say. This is dependent on the relative u values , the area of the loft where the insulation is applied and the expected difference in temperature between the heated area below the insulation and the unheated area above. Also bear in mind that this difference is unimportant when you are not using heating and will only be at a maximum for a very few days of a year.

My own belief based on  my calculations is that there is only about 90 watts difference in terms of heat rate required between having 6" and 8" of insulation.

Rate of heat loss =U Value  of insulation times temperature difference times surface area over which heat loss takes place.

Usually to outside the max temp difference used in Britain is 22 degrees assuming house at 21 and outside at -1.

Surface area of loft depends on size of house but for small semi could be 45 sq metres

u value 6" about 0.3 and 8" about 0.22 gives heat loss of 300 watts and  210 watts respectively.

This saving would only be on the coldest days of the year.

Answer 3

no  

Answer 4

No harm in it. It should retain more heat in your house.