Dormer Window on an Eco House


When I bought the cottage, it already had an attic room with a dormer window. I loved this room when I first saw it, and it was partly what made me buy the house. However, it had turned out to be extremely cold in winter, so unusable as the studio I had dreamed of. It was also too cold to use as a guest room during the winter months.

Fortunately, since improving insulation is a main priority of the renovation, this room will be usable all year round when everything is completed.


What a Dormer Window is

In case you aren’t familiar with the term – a dormer is a window that projects out from a sloping roof (see photo above.) In an attic room, the walls slope, giving less space at full height than at floor level and having a dormer makes the room more spacious. It also means you have a view, which you often don’t with a skylight or other roof window, and gives the room a lighter, more airy feel.

For all of these reasons, I was keen to keep the dormer. As we went through the process of obtaining planning permission, we learned the cottage is in a conservation area and an area of natural beauty, so planning regulations are more stricter than in some areas. The new dormer would have to be the same as before.


Dormer windows – comparing new Eco with old and leaky

As we’ve already seen in previous posts, the quality of the roof is hugely important in an eco-renovation. Compared to an ordinary roof, an eco-roof is more complex in construction. To be properly insulated, the whole roof (Photo of before) had to come off. This wasn’t a big deal because it was old and needed to be replaced anyway.

As was standard at the time, the original dormer window and roof were constructed in a different way to the new one. They were made of single rafters that acted as the load bearing part of the construction. This layer was covered in a weatherproof outer layer, with plasterboard in the inside. Nowadays, in the UK, building regulations do require more insulation, so some sort of insulation would be used in the void. However, the walls and ceiling of the dormer wouldn’t be as thick because they would not use as much insulation as we used.


In contrast, we made our whole construction out of I beams leaving lots of space for the insulation. This is a more time consuming operation, but is much more effective at maintaining an even temperature in the house during winter and summer.

A complex construction

The construction of the dormer window needed a lot of care. It has to be strong, because it is part of the structure of the roof: how the Steico beams intersect is crucial, as we need to fill the gaps, with small bits of wood (as shown in the photograph). We also need to make sure it’s possible to get the blown-in insulation in to all the awkward corners, such as where the main roof meets the dormer construction at an angle. This is the main insulation layer for the roof, so it is important to get right.

Because it had to be integrated into the roof, the construction of the dormer happened in stages. As first the builders created the structure, and then covered it with plastic while they fitted the solar panels. When these were in place, they finished it off.


What to do about the sides of the Dormer

The sides, or cheeks as the builder keeps calling them, of the dormer are covered in lead sheeting. This is expensive, but while tiling with spare roof tiles would cost nothing on materials, labour would be a big cost, because would be fiddly to do. Over the lead is a rubberized roof, which isn’t completely flat so that the rain can run off either sides and down into the gutters.

On the underside of the roof, the builders will eventually fit an insect mesh. This will prevent insects getting into parts of the roof and causing a problem. Insects have loads of places to go in the garden, so it’s not as mean as it sounds.

Although a dormer might seem complicated, and is more expensive that just having a plain roof, it is definitely worth it. Because of the rubberized roof and lead cheeks it won’t leak, and its strong construction means it will last for many years.

Next time we will look at more work on the inside of the house, and the airtight layer. Do let me know what you think so far, I do love to hear what you think, so please make comments.

See you soon.





Fitting Solar Panels on a New Roof


 I was excited to be at the stage of putting tiles on the roof. Not only did this mean the building looked like a house again, but it also meant we were a step nearer to attaching the photovoltaic panels, which was what I was especially looking forward to!

I hadn’t been sure about these, and had planned on having both thermal solar panels and photovoltaic panels. However, the architect pointed out that with just me living in the house this would not be cost effective. Thermal solar panels consist mainly of thin plastic pipes filled with water. The water heats up when the sun shines on the panels. In the summer, I would have far more hot water than I could use, a real waste.

Thermal solar or photovoltaic panels – what’s the difference?

Solar thermal panels are much cheaper than photovoltaic ones because they are much simpler. Some people even build their own panels. On the other hand, although photovoltaic panels are more expensive, their design is more complex and they produce electricity rather than heating water. In the UK, when electricity is produced, it is firstly used by the household. Any surplus goes to the grid and you get paid for that. Depending on your household needs, either type of panel might suit you better. If you use a lot of hot water, the cheaper thermal panels might suit you, but if, like me, your water usage is minimal, then photovoltaics are the panels for you.

Fitting solar panels to a roof

If you add solar panels to an existing roof, they sit on top of it, with a gap between roof and panels. However, because we were rebuilding the roof, we were able to integrate them more. This integration means the photovoltaic panels sit on rigid plastic sheets and are almost flush with the roof, which has two benefits: they look better than if placed on top of a tiled roof and they are not susceptible to high winds. Any rainwater that runs down the roof goes between the panels and the sheets, making them hardy in all weathers.


Before all this happened, we had a few more steps after screwing on the Gutex Boards (which happened in the last post.) First, the builders taped round the edges of the Gutex boards. Then on top, they laid a thin sheet of breathable water and windtight membrane. On top of that went the battening. Battens are thin strips of wood nailed across the roof. The builders then nailed the tiles onto these.


Apart from the dormer, for which the builders constructed a basic shell at the same time as they created the structure for the roof, that completes the outside of the roof. At this time, the dormer was covered in plastic sheeting until it could be finished. There was also work to do inside, putting in the insulation for the roof.


I’ll write more about both of these in later posts, but for now our focus was on preparing the roof for the photovoltaic solar panels. The builders concentrated on tiling the back of the roof, since that was where the panels were going. The architect had worked out the exact position and size for the panels so the builders tiled around the edges of the roof, leaving spaces for the panels.


Ikarus Ltd, the solar panel company, delivered the panels to the site, and then a couple of days later, the big day came. It was time to fit the panels. When I went to the site, it was buzzing with people. As well as my builders, there were people from Ikarus Ltd. Their fitters were on the roof, getting the solar panels in place. First, into those spaces the builders left, they fitted rigid plastic sheets that the photovoltaic panels fit into. Then they attached the solar panels.

An exciting day, fitting the solar panels

It was a lovely, clear winter’s day, shortly after Christmas, and I brought mince pies for everyone. When we stopped to eat the pies and drink tea, I chatted with the people from Ikarus. They spoke about other jobs they were doing, creating solar farms. I felt fortunate to have them fitting in my little job around their vast projects. I felt so optimistic on what seemed like a momentous occasion. Everything seemed more complete, and I could imagine moving back into my house in the near future. Little did I realise that day, there was still a very long way to go.