Winter is coming. The jumpers are out of storage, the thicker duvet is on the bed and I’ve started knitting woolly hats for the family. Those are all ways of insulating ourselves against the cold. But what about optimising the insulation on our buildings?
Of course there is loft insulation, cavity wall insulation and triple glazing. In fact these days, most of us have our homes pretty well wrapped up.
Could you make better use of your buildings if they were insulated?
How about your outbuildings though? The dog kennel, the stables, the garage, the shed where you store the potatoes and apples you harvested this year?
You could even extend the usability of your garden office by insulating that too. And just think how cosy it could feel to sit in the summer house in winter time with candles, hot chocolate and a good book.
Green roofs are great insulators
A living green roof is a surprisingly good insulator. The Vikings knew that 1,200 years ago. They topped their homes with turf. A locally sourced, sustainable product that did the job better than anything else they could find. We seem to be going through a period of reviving ancient skills, modernising them and making the most of them. So let’s take advantage of all the benefits that green roofing can offer.
A sedum green roof is not quite as good an insulator as a wildflower green roof. The deeper the growing medium on your green roof, the better it will insulate. However, there’s a compromise here. Deep layers of substrate (growing medium) are extremely heavy. To hold them up you need a really “beefy” building with a well-supported roof.
Unless your garden building was bespoke made to cope with all that extra loading, it probably won’t take the weight of a wildflower roof. A light weight sedum roof still offers good insulation without the extra expense of bolstering the building.
“U” value of a sedum green roof
Architects and planners work with what they call “U” values for insulating materials. That’s a measure of how much heat can escape through a material into the outside world.
For things like loft insulation and cavity insulation, it’s relatively easy to assign a U value because the material never changes. Experiments and measurements in a laboratory can test the insulation value of the product.
A green roof however, is in a constant state of flux. Sometimes it’s wet, sometimes it’s dry. The plants may be small (as sedums typically are in winter) or they may be tall and have lots or air trapped between the leaves. Plants behave differently at night time than they do in the day and things like the strength of the sun, windspeed and air temperature can affect their metabolism from hour to hour. In short, it’s not possible to assign a U value to a green roof system.
A living green roof not only insulates a building and makes it accessible in the winter months – it is so much nicer to view from a bedroom window that plain old roofing felt.
Science has proven that green roofs insulate buildings
Having said that, scientists have carried out numerous experiments to show that green roofing insulates against heat loss in winter and heat gain in summer. And they have proved that it’s worth the investment.
So, if you want warmer buildings without increasing your energy bills. Green roofing is an option you ought to consider.