Before you begin your loft insulation project be sure to clear out the loft completely and always wear protective clothing and dust mask. Seal any large gaps where pipes or cabling run through the ceiling into the loft. You can use standard expanding foam for this task. cover all recessed lighting penetrations using Downlight Covers, this will enable you to achieve total coverage of the insulation material and seal against cold air infiltration.

Step 1 (insulate cold water tank and pipes)

The cold water storage tank and all exposed piping should be insulated before fitting any insulation material as access will be easier at this stage. if possible, use a proprietary, purpose made, insulated tank jacket to insulate the sides or failing that, roll fibre insulation material around the tank and secure with string. Fit a rigid insulated lid to the top of the tank. Fit proprietary lengths of pipe insulation to all exposed and secure with tape. This will prevent your cold water from freezing up and will also save energy by keeping the supply at a temperature that is quicker for the electric shower to heat. 

Step 2 (lay walk boards / storage area)

A Walkway will be required to access the cold water storage tank area and a storage area may be required for household items you may want to store. This can be achieved with the use of proprietary insulated walk boards. These walk boards are insulated with rigid insulation and, although thinner, achieve the same insulation value as the surrounding mineral fibre insulation or you can just construct a raised  boarded area. You should fit the storage area in an area that is easy to access from the loft hatch and if possible, adjacent to the cold water storage tank for access. Insulated walk boards should be fitted after the first layer of mineral fibre is fitted between joists and prior to the fitting of the second layer of mineral fibre.

Step 3 (lay first layer of 150mm)

Measure the distance between the joists and cut your roll of 100mm mineral fibre to suit. It is best to cut while still wrapped. Starting at the eaves, un-roll the insulation towards the middle. it is good practice to leave a gap between the eaves and the insulation to allow for ventilation in the loft space. At the middle, cut the insulation with a scissors or toothed knife to achieve a clean cut.  it is easier to cut at the centre than at the eaves where space is limited. Start again at the far side and work again towards the middle. Do not lay insulation under the cold water storage tank as this requires the heat from the house below to help keep it above freezing in the cold weather. Again, the cold water storage tank should be insulated to the sides and top. Take care to work the insulation between cables and piping without causing damage. You should always work off boards that you can move along the joists as you progress.

Step 4 (lay second layer of 150mm)

This layer must be cross laid over the joists to eliminate the bridging factor of the timber and create an unbroken layer of insulation. It is easier to work this layer of insulation if it is cut into  manageable lengths. Un-roll the insulation completely and using a scissors or toothed knife. cut into approx 2.5m lengths. push the layer of insulation into the eaves taking care to maintain the gap for ventilation. Again, always, where possible, work from the eaves into the centre

Step 5 (insulate and seal loft hatch)

All loft access hatches should be fitted with draught proof stripping to prevent heat loss through cold air infiltration. Draught proof strip comes in self adhesive rolls and should be fitted to the entire perimeter of the hatch opening (not the hatch door). 4 bolts should then be fitted to the cover to ensure tight closing. Insulation should, where possible, be fitted to the rear of the cover although this may not be possible where a loft ladder is fitted. One method of fitting insulation is to fill a polythene sack with mineral fibre and glue it to the rear of the cover. Alternatively, you could cut a piece of min 70mm rigid insulation and fix it with glue to the rear of the cover.