Sunday, 4 October 2015


To get the result you hoped for from installing energy efficiency and renewable energy measures, it is important to get the detailing right. Not doing so can result in losing a lot of energy from unexpected places, or the products and systems not working correctly. However, it can be very difficult to know how much all these details matter, indeed what the details should be, and how much effort to put in to persuade the builders to use particular products or do things in a particular way.

We have made two detailing decisions recently. The first was about finding a special sealant for the junction where the waste pipe from the loft shower room goes through the side wall of the house and, importantly, through the Pavatex external wall insulation. The standard builder's solution would be to seal around the outside using silicone. However, we weren't sure if this would be good enough for the Pavatex. As it is a wood fibre insulation, it's obviously very important it doesn't get wet. So, I looked through various technical documents and web sites, found what seemed to be the recommended joint sealant (a tape called ISO BLOCO 600), found a UK supplier and ordered the tape. This took upwards of two hours, and a couple of days later some rather modest looking tape arrived in the post. Was it worth it? Let's hope so.

The other detailing decision required less time staring at a computer screen. My husband removed the row of floorboards closest to the outside wall in bedroom 1, and installed insulation adjacent to the external wall between the ground and first floors. We had some hemp batt insulation left over from insulating underneath the ground floor years ago, and used this, cutting it to size. It means there shouldn't be a cold section of wall between the ground floor (internally insulated to ceiling level) and the first floor (internally insulated to floor level). With a detail like this, we'll never see the effect in terms of energy bills, but it definitely seems worth doing.

Sunday, 27 September 2015

The art of compromise

Insulated plasterboard below tiles
As our major building work is winding up , we are having some small repair jobs done. One of these involved removing a broken fan from the wall of our family bathroom, which revealed the insulated plasterboard we had installed on the the inside of the external wall more than 10 years ago. I had completely forgotten we had specified this - it was in the days before we had ever considered 'proper' solid wall insulation , and was a low effort, and probably low reward, means of trying to save some heat.

The list of solid wall insulation material we have used is varied, reflecting largely the level of disruption and expense we could cope with at the time:
  • external side wall of semi, ground and first floor - 100mm Pavatex 'Diffutherm'
  • internal walls front and back of the house, ground floor living space - 60mm Pavatex 'Pavadentro'
  • internal wall back of the house, first floor bedroom 1 - 70mm Pavatex 'Pavadry'
  • internal wall front of the house, first floor bedroom 2 - 4mm Wallrock KV600 thermal liner
  • internal wall, first floor bathroom - 10mm expanded polystyrene
Some of these products come with detailed data sheets, specifying U values, and offering guarantees. Others either came with nothing, or rather optimistic claims about energy savings. The thermal wallpaper in bedroom 2, for example, is unlikely to save a great deal of energy. However, the main purpose of installing it was to stop condensation and mould growth, and it has achieved this.

One thing I have learned from the gradual eco-renovation of this house is to accept that decisions are made at a particular time, with limited knowledge, limited energy  and a limited budget. It is often not possible to choose the best solution in terms of energy saving.  Compromise is inevitable. In fact, compromise is probably not the right word, as energy saving is not the only goal. Even for people who are keen to reduce their energy use, there are other priorities, and many practical constraints to choosing the lowest energy solution. As so often in life, a good compromise may be the best we can achieve.

Friday, 18 September 2015

Bring me sunshine

Our PV system was connected up last night, and is currently happily generating electricity. The PV system comes with a smart meter, an electricity display system and an online account, which I haven't explored yet. The display system is very easy to understand - but difficult to photograph, being very shiny. Here the picture shows the power the panels are generating - 1.20kW - this compares with a maximum power rating of 1.96kW.  Watching the numbers go up and down as the sun emerges from and goes behind clouds can get hypnotic.

Many thanks to JoJu Solar for a very professional service in designing and installing our system.

Friday, 11 September 2015

Two uses of light

Our triple-glazed windows are now fitted into the window frames, with just the external cover strips left to attach. They are very nice looking windows and, most importantly, fit the holes available.

Solar PV
PV panel specification
Our solar panels have now been attached the front roof of the house, which is west-facing. There are six of them, adding up to just under 2kW capacity - 1.962kWp to be precise.  Together these are estimated to generate 1,626kWh per year - which is around 200kWh per year less than our typical annual electricity consumption. So even though this is a small system, we are almost generating enough electricity to meet our own needs. They have been fitted by JoJu Solar. Next week the electrical connection to the panels will be attached, and electricity will start to flow.

This is our third renewable energy system, after the solar water heating and a wood burner, but the only one that is visible to the outside world. Although, via Superhomes, we have been promoting our house as an eco-home, it's never looked particularly different to other homes on the street before - which I quite liked.

But there were half a million solar roofs by 2014, so it's not an unusual sight these days, and indeed our system is considerably smaller than another PV installation up the road. So, no need to feel that we're investing in ostentatious eco-bling, just a normal part of the UK street scape.

Friday, 4 September 2015

Windows, walls and a staircase


Today our triple glazed windows have arrived from Estonia. They made it all the away across Europe, and are now sitting in our conservatory looking very lovely. They are the size specified (big sigh of relief), the right colour and seem to be just what we had hoped for. The insulating fixing foam has also arrived. Just the installation stage to get over next week, and then we can start enjoying them.

Being triple glazed they are heavier than normal windows - with the larger one being over 80kg - it's lucky we have helpful (and strong) builders to help move them.

Insulation before and after plastering
The Pavadry solid wall insulation has now been added to the first floor bedroom. The plasterer who installed it had worked with lime based plasters / adhesives before, so he was happy installing it. Lime plaster / adhesive is used between the bricks and the Pavadry, with plasterboard and a skim of conventional plaster on top. He's done a lovely, neat job. The only sign that it has been installed is that the walls are now 70mm wider than they were before - meaning there is an extra width of reveal around the window.

We now have a staircase between the first floor and loft rooms, most of the plastering is done, and the second fix of carpentry etc will be beginning next week.

Solar PV
Installation should begin next week. The scaffolders who were supposed to turn up today haven't, but hopefully they'll be here early next week.

Friday, 21 August 2015

A car's worth of insulation

Having resolved our supply chain issues, we brought home a full car load of insulation yesterday. Soon this will be attached to the formerly grotty wall of the children's bedroom, and it should be a much cosier space.

At the builder's merchant, my husband met an NBT representative who talked him through the justification for using conventional plasterboard in conjunction with the Pavadry materials. Apparently it's all in the technical manuals. I understand there's an acronym for that, but he was far too polite to use it.

Monday, 17 August 2015

More solid wall insulation

In addition to having the loft converted into a bedroom, for use by our daughter, we are also upgrading the insulation in the bedroom she currently shares with her brother. This room is on the first floor, and already is insulated externally on one external wall (the side wall of our semi-detached house). However, unlike on our ground floor, there is no solid wall insulation on the other external wall in this room. This cold wall is still prone to condensation and mould in winter.  Which is obviously not what anyone would want in a child's bedroom.

So, we are going to have internal solid wall insulation fitted to the uninsulated cold wall. For this we are going to use 'breathable' materials, as we did for solid wall insulation in the rest of the house (but not the new loft conversion work). This involves us specifying and ordering Pavatex woodfibre boards (Pavadry), plus the fixing and taping materials, so our builders can install them.

This isn't as simple as you would hope, in that the product suppliers (NBT) don't deal directly with individuals, so we have to go through another builders' merchant. There has been some back and forth about which organisation can provide price quotations etc. Hopefully, somebody will take our money at some point, and we will get the products on site, on time.

The product range seems to have moved on since we used earlier versions of this product in 2009/10. For example, it is no longer required that the finishing layer of plaster be lime plaster. Instead it can be finished with standard plasterboard. This makes it easier for conventional builders to install - as most will have no experience with lime plaster. It seems a little odd, since we were persuaded on the lime plaster arguments with the previous product.  However, I haven't got a moisture movement model, or the knowledge to use one, so I am going to assume the manufacturers have done the calculations and that using gypsum plaster / plasterboard will not be detrimental.

In the main loft conversion, all is going well - with work on pause for a few days, until the staircase is installed and the loft room connected to the rest of the house.