Many houses, such as the numerous Victorian terraces in Stafford, cannot be insulated with cavity wall insulation as they have solid walls. As much as 40% of the energy used to heat these houses can go straight out of the walls. When I bought my three storeys Victorian terrace I was determined to tackle this problem. I had been renting the top two storeys for some years before buying the house so I knew how poorly insulated it was. The large loft room in particular was a nightmare to heat and was almost unusable through the winter. It also prevented me from using standard loft insulation. I had never renovated a house before so the whole thing was a bit of an experiment, however I had help from my more experienced father. By setting out what went right and wrong, what I learned, I hope that this case study will help anyone else that chooses to do a similar job.
Insulating the walls and ceilings
There are basically two methods to insulate solid walls – external or internal. As I was renovating the whole property and the disruption caused would not be a problem, I chose an internal method. Rather than standard dry lining I used a phonelic foam-backed plasterboard bonded to the wall. The board is called LaFarge Thermalcheck K and is only 40mm thick (30mm of insulation foam and 10mm plasterboard). This was chosen mainly with the loft in mind, as I would be insulating sloping ceilings and wanted to maximise head height in certain areas. The phonelic foam is a very good insulator and the 30mm of foam is equivalent to a much greater thickness of rockwool or polystyrene.
Kitchen: no sweat
The first wall I chose to do was a vertical kitchen wall. The foam-backed board is bonded to the wall using a special adhesive that I bought along with the board from Simmons of Stafford. Dabs of the adhesive are placed on the back of the board and it is then put in place against the wall. To comply with building regulations it is also necessary to ‘mechanically’ secure the board to the wall. As I needed places to hang kitchen cabinets from I chose to put up 30mm treated wood batons where the cabinets would hang. I then cut the foam off the back of the board where the batons were (an easy job with a sharp knife) and nail the board to the batons. This system worked well and was quick to do.
Loft room: trouble with lath and plaster!
The next room was the loft room. After the success of the kitchen I thought this would be easy too. I first did the two end walls the same as in the kitchen but used vertical batons. The board was easy to cut to shape for the various slopes and again the job was quick. As I became more familiar with the materials I was more careful to apply a perimeter of adhesive to the board to seal out any drafts from behind.
The sloping areas of the ceiling were next and this is where I should have done things differently! The first mistake was to leave the lath and plaster in place. I thought it would be a big job to remove it all and wouldn’t be worth the effort. My plan was to nail through the board, through the lath and plaster and into the roof joists using 80mm galvanised nails for a secure mechanical fixing. This would be more important on the slopes as it would need to hold the board whilst the adhesive set overnight. Although the method worked it was difficult, hard work and there were a series of problems. It was time consuming to work out where the joists were and then to transfer that information into lines on the board so I could nail along them, the slope and large nails caused a problem when hammering that was even worse when it came to the ceiling area and the poor quality of the lath and plaster meant often the boards did not go on flat and even larger 100mm nails were sometimes required. Often the nails would puncture the paper covering of the plasterboard and not hold the weight or the boards would sag and needed additional support in the form of props until the adhesive set. However I was pleased with what was achieved and could immediately feel the improved heat retention in the room.
A significant improvement
I have subsequently done another sloping ceiling but removed the lath and plaster first. It was not a big job, although messy, and made things significantly easier. It also gave me a chance to insert an additional layer of medium density rockwool insulation (50mm) from Wickes between the roof joists. I also changed to using dry walling screws as I had purchased an electric screwdriver – this made life far easier and solved many problems. This room is a bathroom with much more space to spare but with three external walls and the sloping ceiling. In this room I added additional insulation to the walls as well by using 50mm batons with medium density rockwool between them and the Thermalcheck K screwed over the top similar to traditional dry lining. This was more time consuming and expensive but did give me the additional insulation I was looking for to make a warm bathroom.
Unfortunately I am unable to give any energy efficiency figures as I have also installed a central heating system, double glazing, underfloor heating and other measures but from my experiences of the house prior to my renovations I know it has been significantly improved and now retains heat well in the winter.
Photos coming soon