Issue 4 - Reducing heat loss through Roofs (Part 1)

Issue Date : 26th May 2009

Welcome to the Newry Democrat’s renewables and energy saving section brought to you by Kellys Renewable Energy Solutions (www.kellys.uk.com).  This week we shall look at ways of reducing heat loss through your roof.  Up to 25% of the total heat loss of a house is through the roof.  This week we will focus on a pitched roof without a room in the attic and next week a pitched roof with a room in the attic.

Pitched Roofs without a Room in the Attic

It is normally straight forward to install insulation into these types of attics as insulation can be placed between and over the joists of the flat ceiling of the rooms on the top floor. Where insulation is already present and more is required to bring it up to the latest recommended level, current advice is to leave the existing insulation where it is and place new insulation over the top, laid at right angles to the existing.

With most existing properties, 100mm of mineral wool insulation has already been installed. To achieve the current recommended U-value (rate of heat loss, the lower the U-value the better) of 0.16W/m²K using mineral wool, 275mm would be required. An additional 175mm would be required to meet the recommended U-value. Alternative renewable products include sheep wool, hemp (from the hemp plant) or cellulose (recycled newspaper).

When the thickness of loft insulation is increased the temperature in the attic is reduced, meaning water tanks need to be protected from freezing. Omitting the insulation beneath the tank but returning up the side and over the top helps prevent freezing.

This type of attic is ventilated at the eaves. It’s important not to block this path of ventilation with insulation, causing condensation.

A last point is not forgetting to insulate and draught-proof the loft hatch.