What is the difference between a Brown Roof and a Green Roof?
We have a ‘brown’ roof rather than a ‘green’ roof on our modern farmhouse. This means that instead of putting for example a sedum ‘carpet’ on the roof which dictates what will grow on the roof eventually, we have only covered it with soil (the soil that was on the ground before we built our house) and let nature decide what should grow there! (I did sprinkle some wild flower seeds over the roof last year but it was so dry afterwards that nothing grew!)
We are really pleased with the variety of flowers that we have for the moment (June). Especially the white clover attracts loads of honey bees and bumble bees, which is just how we had imaged it!
Types of plants found on our roof after 1 year
Grass: we have a lovely variety of grass on our brown roof, most of the different types self-seeded, but some of them were planted by us a year ago; those have not spread at all, though.
Moss: again – lots of different types, especially where the soil is too dry for any other plants to grow.
Flowers: Daisies, Fox-and-Cubs, Pyrethrum Daisy (planted by us last year and growing really well), Red and White Clover, Nigella (one! Maybe the only survivor of the seeds I sprinkled over the roof last year…), Potentilla (planted by us, waste of money as it doesn’t spread and doesn’t look particularly nice), sedum (one plant planted by us this month, will have to see how it grows and report back next year), gorse (self-seeded), as well as lots of other plants that unfortunately I don’t know the names of.
For more information about wild flowers and a monthly overview of what grows wild here in England have a look at this website: www.seasonalwildflowers.com.
White Clover with bumblebee
Various types of grass
Various types of grass
The ‘shell’ of our house, i.e. the walls, floors and roof, is made from panels that contain sheep wool insulation. Although we have our own sheep on our farm we could not, unfortunately, use their wool as this would have been much more expensive than buying the left over wool from carpet manufacturers.
Wool for carpets is brushed, and what cannot be used for the manufacture of carpets is what goes into our walls, hence the different colours!
Wool is a brilliant insulating material (as we know from wearing woolen jumpers!) – it has loads of tiny air pockets which traps the cold air, which is why the wool is not packed in too tightly into the panels. Wool absorbs and releases moisture without impacting on insulation properties (unlike cellulose insulation). It is also supposed to be a brilliant acoustic insulator, which is something that we will be able to confirm once we have moved in to the house, as we have used the wool in internal partitions where we needed an additional noise barrier Before it can be used in walls it has to be treated with borax to enhance its fire protective qualities and to protect it against moths and other pests. Needless to say it is a very eco-friendly building material as it can be used over and over again and will not harm the environment once it has been disposed of.
Panels are made from OSB sheets.
Exterior face of the OSB panel is painted with water resistant paint.
Every panel gets a number which corresponds to numbers on a computer generated model of our house; when the builders are ready to install the panels each panel has an exact position it needs to be in. The (floor) panels slot easily into place and rest on the glulam beams as shown on the image below:
Once all the floor, wall and roof panels have been installed the joints are sealed on the inside of the house to help make the building air tight. The tape we used was incredibly strong, you can get it here from Tapes Direct!
Installation of the panels only took a few days as everything is put together like a LEGO house!
What is glulam?
The frame of our house is a glulam frame. Glulam is basically several layers of timber (laminates) glued and pressed together. Hence – glu(e)lam!
Glulam beam, different pieces of timber visible.
This makes it 18% stronger than an ordinary timber beam and also allows the beam to be bent, thus creating many possibilities for unusual designs. The timber comes from Scandinavian sustainable forests and the ‘manufacture, distribution and treatment of glulam all consume less energy than any other building materials’ (according to www.glulambeams.co.uk) and is therefore more environmentally friendly than steel or concrete beams. Glulam is also light, easy to handle, fire resistant and, if treated correctly, very durable.
Two beams joined and glued together to make one long beam.
Glulam posts and beams
The posts were installed on the concrete pads I wrote about in my last blog (www.timeandspace-interior.co.uk/pad-foundations-of-our-eco-house/) with galvanised steel feet and bolts. The glulam beams were then installed and fixed to the posts using stainless steel bolts. Each post and beam has been designed on the computer, so when they arrive on site it is very easy and quick to assemble the glulam frame.
Overview of our glulam frame
Our architects recommended we build our house on pad foundations instead of strip foundations, which are more common. The advantage of having pad foundations are that you use less concrete (each pad is between 450x450mm and 800x80mm wide and at least 300mm deep) which means it is more environmentally friendly and cheaper as you use less material. By using pad foundations you also disturb the ground less than you would with strip foundations.
Excavation for a pad foundation
As the structure of our house is made from glulam posts and beams, we have one pad under each post. We also have some strip foundations, mainly along the external walls. When 2 pads were close together we merged them into one, keeping the specifications of the bigger one.
Levelling the concrete in a pad foundation
Below is a picture which shows how our house is built on posts – each post has a foundation pad below it. Due to the slope of the ground the finished level of each pad had to be carefully measured, although the posts can be slightly altered as they sit on galvanised steel ‘foots’ that are fixed to steel plates, which are bolted to the concrete pad.
Post with ‘foot’ and plate (not yet bolted onto concrete pad foundation) to allow for approx. 25mm leveling.
If you want to know more about foundations click here for a clear and comprehensive website.