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.

Tuesday, 11 August 2015

Spaceship loft

Work is continuing with the loft conversion. Much of the internal insulation has now been installed. It is made up of two different materials - Xtratherm, a rigid polyurethane foam board, overlain with a silvery space blanket material.

For the ceiling / roof level insulation the builders have installed 100mm of Xtratherm, and 80mm for the 'dormer cheeks' (the side walls of the dormer).

Excitingly, this is very much how the future was meant to look. Less excitingly, this shimmering, spacey look is being covered by plasterboard - which I don't think has ever been accused of looking cool or futuristic.

We are looking into whether we can add extra insulation into the spaces created for fitting the LED lighting. This might be possible if we can specify LEDs which can be surrounded by insulation, or by using lighting covers. The additional insulation isn't part of current practice, or needed to meet building regs, but it would be a good thing to do if possible.

Today we also had a visit from an Energy Performance Certificate (EPC) assessor. In order to get the government payment for generating renewable energy from our PV panels (known as the FiT - Feed In Tariff), it is necessary to have a home which achieves at least D on the EPC scale. We should find out the result in a couple of weeks - according the scheme rules, assessment needs to be delayed until the staircase has been built into the loft room.

Tuesday, 4 August 2015

Loft conversion

We are currently having our loft space converted into an extra bedroom. Many of the details are just as required by Building Regulations, but we are having higher specification windows and wall insulation. We have chosen triple glazed windows, to improve heat retention. There are two triple-glazed Velux windows, already installed in the sloping roof and two triple-glazed windows for the dormer window on order from a factory in Estonia. Our insulation will be extra thick on the side wall of the house, as that has existing external solid wall insulation, and full internal wall insulation will be installed in addition.

We are also using metal guttering and down pipes rather than standard PVC.

Windows: easy and difficult
Ordering the triple-glazed Velux window was very straightforward. However, specifying and ordering the other windows has been a long and somewhat fraught process, requiring extensive discussions between our builder and the specialist company we used to order the window, as to precise sizings and particularly the fitting system and materials needed for that. Our builder assures us that windows are always difficult because every manufacturer uses a different fixing system, and windows all have different details. Nevertheless, it has brought into sharp focus, yet again, how difficult it can be to specify components which go beyond current standards.

Solar PV
We are also going to have some solar PV fitted to our west-facing roof - as the (smallish) south facing roof already has solar water heating on the higher part, with the remaining roof area being over-shadowed by buildings and trees. We were debating having additional PV panels on a south facing frame on our new flat roof (on top of the new loft dormer). But this would require planning permission, because the highest edge of the frame would be above the existing ridge line - as opposed to putting a full set of panels on the street-facing roof which requires no planning permission. Planning permission could take up to 8 weeks to come through, and might mean we wouldn't be able to take advantage of the existing scaffolding (which will save some costs, and hassle). Also there were rumblings from our builder about our flat roof guarantee being compromised - although the solar firm said they could do the installation without affecting the integrity of the roof. So we have taken the path of least resistance and gone for the smaller west-facing system only. The panels will still generate almost as much as our current electricity consumption.  In comparison to the windows saga, dealing with the PV company has been very easy. They are specifying and fitting everything, much to our relief.

Wednesday, 15 July 2015

The purpose of this blog

The purpose of this blog is to share the experience of renovating an Edwardian home. We are renovating it in order to reduce energy use and carbon emissions, and to create a more comfortable living space.

We are part of the Superhomes network, and you can see more material about our house here:

Renovation story 2009-2010

These are the
blog entries I wrote during an earlier phase of renovation, 2009-2010, previously hosted on the ClimateX website, which is no longer maintained.

Oct. 01, 2009
We live in an Edwardian semi in Oxford and are about to begin eco-renovation works. The main work will be installing underfloor insulation under the wooden floor downstairs, insulating the side wall of the house externally and the front and back walls internally. We will be using paper-based insulation under the floors and wood-fibre insulation (Pavatex) internally and externally. The external wall will be finished with a lime render.
Previously we have installed additional loft insulation, double glazing, draft proofing, extra floor and wall insulation in an extension and solar water heating. Hopefully this work - as well as sorting out some (isolated) woodworm, condensation and slug(!) problems - will make the house much more cosy and considerably reduce our energy use for heating.

Oct. 06, 2009
Day two and despite some disappointing weather (following a long period of drought), the installer is making good progress.  One of the plus points about Pavatex is that it is bio-degradable.  This makes a difference during the installation. Instead of lots of polystyrene drifting around the garden (previous experience), we're hoping to chuck all the small offcuts onto the compost heap.

Oct. 08, 2009
At the end of the fourth day of working, all the external insulation has been fitted to the side wall of our house and work has started on rendering to make it water-proof. We have added 100mm of Pavatex woodfibre, which when combined with specific render is called 'Diffutherm'. The Pavatex is 'made from over 95% waste softwood and under 5% inert water proofing additives'. When added to our solid brick walls, the U value should improve from around 2.4 W/m2K to 0.33 W/m2K. This is about the same standard of insulation as required by Building Regs for new homes in 2002.
In any case, you can certainly feel the temperature difference between the insulated side wall and the uninsulated (as yet) back and front. All has gone very smoothly so far - even the scaffolders turning up a day late didn't cause major problems. 

Oct. 21, 2009
After the first layer of render was completed at the end of Week 1, Week 2 involved simply waiting for the render to dry. Tomorrow, unless there is torrential rain, our contractor - Merl Cunliffe - will be coming back with a colleague to put on the final layer of render. This all has to be done in one day, to get a good appearance. After that layer has dried, it will be painted. Then there will be some further work in extending the roof by a couple of tiles, to protect the top of the insulation from rain.
The materials for the external insulation have cost around £3000. Merl will work for 7 - 8 days in total, there will be some additional labour in extending the roof tiles, and the cost of scaffolding to add on top. Not surprisingly, this will end up costing many times more than getting insulation blown in to cavity walls. If I recall correctly from a previous home, that took two men in a van about three hours to complete (for all the flats in a block of four) and cost a subsidised £50. Happy days! I blame the Edwardians...

Oct. 29, 2009
Unfortunately preparing our front room for internal and underfloor insulation involves making things far worse before they get better. Plaster has been removed from the walls where insulation will be added, the ceiling coving has been removed temporarily and all the floorboards are up. As well as being necessary for adding the underfloor insulation, floorboard removal also allows proper inspection of all the existing underfloor timbers and checking for damp etc. As the existing joists are not in the best shape, and already extensively patched we'll probably be having new joists installed early next week. I suppose the real suprise would have been no unpleasant suprises under the floorboards...

There is still some debate about what the best form of underfloor insulation will be - the decision really depends on what the damp specialist finds. If there is a damp problem then paper-based options would be ruled out. Hemp might be suitable - we'll just have to wait and see.

Nov. 05, 2009
Our underfloor insulation has arrived and is now sitting in a big stack in the dining room. As pictured, a first section has been installed in the front room. It is a hemp batt - not the Warmcell waste paper-based insulation we had thought we might be having. The damp in the walls below our damp proof course has meant that Warmcell isn't suitable. The hemp product is a bit more expensive, but will still give a good insulation result (see for technical details). It'll be good when we have floorboards again, but for the moment we're at the stage of admiring our lovely new joists and other load bearing timbers and imagining how cosy it'll be when the job is finished.

Nov. 15, 2009
Our underfloor insulation is now just about complete. It was installed by attaching netting hammocks (as they almost certainly aren't known in the trade) to the floor joists to hold the insulation, and then cutting the hemp batts to fit. The hemp has been installed to the full depth of the joists - so that's 150mm in the living and dining rooms and 100mm in the hallway (where the original joists were retained, as they were in reasonable condition). While the floors were up, the central heating pipes were insulated - they previously had no insulation around them at all! New airbricks are also being installed in several places below the floor level, to ensure adequate ventilation. This should ensure when the floor is next taken up - hopefully not for many, many years - the joists are still in perfect condition.

Our internal walls (i.e. front, back plus an overlap with external insulation to eliminate any potential cold spots) are now ready for installing the insulation. Firstly the existing (gypsum) plaster had to removed. Then a layer of lime plaster has been added to make a smooth surface on which to attach the Pavatex insulation. The major reason for removing the original plaster is to ensure problem-free moisture movement within the insulated wall (the insulation system is only guaranteed if conventional plaster is removed). 

Outside, the roofers have been working on extending the roof to cover the external insulation; the slates look to be a good match, and there's just one half of the verge to be sealed with mortar. Fortunately, despite yesterday's gales, the roof is still attached to the rest of the house - perhaps due to the starring role of the clothes pegs.  Our builders have been doing an excellent job of keeping most of the house habitable during the renovation work, but we're now looking forward to the switch away from 'creative destruction' to re-instating our walls and floors.

Nov. 23, 2009
We are now half-way through the installation of the Pavatex internal wall insulation. Work has been completed in the dining room, just the living room to go. The insulation is 6cm thick and is installed by screwing onto the wall, using insulated screws to fix it in place. We had wondered how it would look to add this extra thickness internally - but even before plaster has been added on top it looks great. It may be partly psychological - but the room does feel cosier already. Certainly, not having a radiator in the dining room (temporarily removed) hasn't been a problem - the heating drifting in from the hall and kitchen have kept us perfectly warm. Not only that, but since the floor insulation has been finished we no longer have any visiting slugs! 

Given that it looks like the adding internal insulation isn't going to look 'wrong' in the house, it does make me wonder whether we should have thought more seriously about going for completely internal insulation rather than external insulation on the side wall, and internal on the back and front. However, the external insulation is thicker - 10cm - and we wouldn't have wanted that thickness internally. It will be interesting to look at the costs of the external vs internal insulation when all the bills have come in. 

Dec. 09, 2009
A lot of progress has been made in the past week and a half. All the internal insulation is now installed, there is a first coat of lime plaster on all surfaces, and a final coat on some areas. Insulation has also been added within the mini 'roof' space above our living room box bay window and an area of the living room ceiling which was in poor condition has been replastered.

In addition, we have had new wooden double-glazed sash windows installed in the box bay, as it made sense to do this in conjunction with insulating around the window area. Several years ago we had the rest of the sash windows replaced with modern double glazed ones, as they were not in great condition, draughty, prone to condensation etc. At that time we decided against replacing the ones in the bay, due to cost. However, we have had to resort to plastic film over the bay windows in winter to cut down draughts (despite having had them 'professionally' draught proofed) and reduce condensation - which would hardly be a good look in a supposedly eco-renovated property. So new windows it is! They do look very nice and that area of the room is much cosier than it was - even before the radiator has been replaced.

Today a man came and created new ceiling cornice to replace what had to be taken down to install the insulation. It looks very good. Another nice period detail which has been retained is a cutaway shape in the walls next to the bay window (see photo, which will explain this better than I can).
The main work remaining inside is to put on the final coat of lime plaster in most areas, put the radiators on, add, sand and seal the wooden floor on top of the existing hardboard and other finishing details. Outside, work has started on adding conventional external insulation to the bottom part of the wall, below the damp proof course, where eco-materials weren't suitable.

It certainly feels that we're nearing the end, and that by Christmas all of the major work will be complete.

Jan. 05, 2010
Before Christmas most of the remaining work on our insulation was completed, and we were able to start living properly in our home again. As well as the insulation work, we had a new British oak floor fitted, to replace the somewhat battered and woodwormed previous floorboards. It looks rather lovely, as do the insulated walls and details around the windows and ceilings. I doubt anyone would notice we've had internal insulation added, unless we pointed it out.

We're very keen to find out how much energy the added insulation (and much improved air tightness) is saving - but it's too soon to really know as the builders only left the week before Christmas. However, our heating and hot water energy consumption in the two weeks before and after Christmas was more than a quarter lower this year than last - and clearly this year is much colder! Still, we'll need rather more time to monitor 'after' before we can say how much energy and carbon is being saved.

I was speaking to a neighbour with a house of a similar age, and she said they were really having problems keeping the bedrooms in the old part of the house warm enough overnight in this cold weather. Their temperature was dropping to 12C - whereas I don't think our has dropped below 16C (with the rooms generally at 18C when the heating is on). We have bought a couple of temperature data monitors, so should have proper data on this soon.

June 06, 2010
The major work on our home was finished almost five months ago, with most of the little bits and pieces completed a few weeks ago, and only the inevitable final bits of re-decorating waiting to be finished.

Now that memories of the disruption of the renovation work are less vivid, it's a good time to write about just how pleased we are with the changes. To start with - the energy and carbon savings have been substantial. Comparing the first two months of this year with last, we have saved 20% of our gas consumption, which I would estimate means the insulation work has resulted in a heating energy saving of 30%. This is probably a conservative estimate, in that this year was colder than last (so more heating energy needed to achieve the same internal temperature) and I haven't corrected for that in the 30% figure. We'll keep monitoring over the coming months and see how that figure develops next heating season.

Secondly, I would say the house is definitely more thermally comfortable - even though we've ensured we haven't raised our internal temperatures. The walls aren't cold any more, there are no draughts from the floorboards and the temperature stays very constant. Even at the coldest part of the winter, when our heating was off overnight, the room temperatures only dropped by at most 3 degrees Celcius. 

Thirdly, when we walk back into the house after being away for a couple of days it smells faintly of new wood. Prior to the work, it used to smell slightly of depressing damp. The eco-renovation work (and associated work) has definitely resolved our damp and condensation problems.
Another benefit, almost beyond price, has been the total lack of slugs since the work! Given how well the floor insulation was detailed, this is not really a surprise. Although, I wouldn't really put anything past slugs...
On to cost - this has not been a cheap exercise. If we add together the cost of external and internal wall insulation and the underfloor insulation, and compare it with the energy savings, the payback period is greater than one hundred years. That is assuming no addition to the capital value of the house, present day gas prices etc. 

The cost of the external wall insulation worked out at around £150/m2. Internal wall insulation may have cost as much as twice that - but those figures are very difficult to work out as we had a lot of other work done at the same time by the same people, and most of the cost was related to labour and not materials. I think our internal insulation costs were particularly high because of the period features we retained, and the fact that this was a fairly new area of work for some of the people involved, and they were having to learn as they went along. The good thing is that I am convinced the work was extremely meticulous and of very high quality - but we have had to pay for that attention to detail. Hopefully, as expertise in the sector grows, prices will fall.

Overall, we are very happy with the work that has been done. Of course it would have been great if it were less expensive - but the cost was in line with our expectations - and it has had important benefits beyond just the energy savings which were our main goal. We are hoping others can learn from our experience and will be opening our home as part of Heritage Open Days, 11 and 12 September 2010.