1.  Existing rafter
2.  Existing masonry wall with timber wall plate
3.  Airtightness membrane
4.  Airtightness tape sealing between airtightness membrane and rafter
5.  Insulation above and below airtightness membrane
6.  Parge coat to external face of wall
7.  Individual rafters lifted with hydraulic jack
8.  Airtightness membrane fed between rafter and wall plate

With bere:architects’ Retrofit for the Future projects one of the most difficult details to realise on site was at the eaves where the airtightness layer in the loft was sealed to the parge coat on the external walls. This is a common and problematic detail for many retrofits seeking to reduce draughts in this area as it is crucial that the membrane remains airtight whilst passing around the rafters to seal to the wall. In our original detail, we showed the airtightness membrane cut around and taped to the rafters and to the parge coat on the wall. On site, this proved to be a time consuming and awkward process and the site foreman suggested that on future schemes it would be more straightforward to individually lift the rafters to allow a continuous airtightness membrane to be passed between the rafters and wall plate, thus avoiding the need for taping. To achieve this, the fixing between the rafters and the wall plate would be sawn through and a hydraulic jack used to lift the rafters free from the wall plate. The implementation of this technique would save time on site and ensure draught-free construction in this area. Eureka moments like this form a significant part of the lessons learnt from these retrofits. bere:architects are working with the Institute for Sustainability and the Technology Strategy Board to further disseminate the lessons learnt from this project.

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78 Grove Road the final retrofitted property

Louise O'Donnell at the front door of the recently completed retrofit

Tom and Louise are now enjoying the comfort of their new passivhaus-modelled retrofit. We have thoroughly insulated their home, fitted new windows, eliminated all drafts and fitted a heat recovery ventilation unit with pollen air filters. The work was funded by the Technology Strategy Board’s retrofit-for-the-future programme.

The elderly tenants, Tom and Louise, have not been at all well. They both have serious lung problems that send them in and out of hospital. Tom’s problem is particularly acute. He cannot walk far and uses an electric buggy and receives regular air quality updates as his respiratory problems are medically linked to air quality problems.

Tom & Louise live right on the  junction where the A315, the A4 and the A314 come together, right beside Heathrow Airport, the South Circular Road, the M4 Motorway and the Great West Road. There is a clear link between air pollution from road and air transport and the chronic lung disease that they both suffer from.

As expected, Tom and Louise are thoroughly enjoying the new comfort that they are enjoying. They talk about the indoor temperature being very even. Whether it is hot or cold outside, they always feel comfortable inside. Tom says how nice it is to be able to get up in the night and walk to the bathroom in his pyjamas without feeling frozen.

But what we only dared hope for, also seems to be happening. As the air quality inside the house has improved, and the particles in the polluted air are removed, Tom told us that his lung problems seem to be improving. He said it is too soon to be certain whether the better indoor air is going to give long term improvements to his condition, but he is already feeling a lot better.

Grove Road

We are absolutely delighted to witness the restorative effect of our work on the lives of Tom and Louise. This case study adds to the mounting evidence of the harmful effects of poor air quality in London. This is a problem that the current government and the London mayor appear to be oblivious to. Only three days ago, it was reported that the conservatives walked out of the GLA as Darren Johnson called a motion on the London air pollution crisis. http://www.london.gov.uk/moderngov/mgConvert2PDF.aspx?ID=5951 Also learn more about the issue by reference to:  http://www.cleanairinlondon.org/

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78 Grove Road near to completion

The Scaffolding has come down at Grove Road and we can now see the building is almost complete. We think that the retrofit has greatly improved the appearance of the house and all involved at the house and Hounslow Homes, are very happy with the results of the work.

This week also saw the third airtest to the property .The property achieved an airtightness of 1.5 airchanges per hour (ach-1). This is a significant improvement from the previous airtest in which the building achieved an airtightness of 2.45 ach-1. Hounslow Homes still have some work to do to improve the airtightness of the property (see previous post) which we hope will bring the airtightness down to 1 ach-1, a requirement of the Passivhaus Enerphit standard we hope the house will achieve.

Even if the property does not achieve the desired 1 ach -1 the elimination of draughts achieved by the work will still be a vast improvement for the O’Donnells and represents a major reduction in the heating demand of the property. With this level of airtightness the Specific Space Heat Demand as modelled in Passivhaus Planning Package would be 27 kwh/(m2a) compared to a pre-retrofit of 494 kwh/(m2a).

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The rear of the almost complete property with scaffolding still in place.

Next week will see the third airtest at Grove Road.This was due to be the final airtest but because of delays related to the installation of a satellite dish the final airtest will have to occur at a later date. The satellite television company have not been able to install their satellite dish for a number of weeks, this has delayed the striking of the scaffolding. The scaffolding needs to be removed before the digging of the trenches for the below ground insulation can proceed.

Once the trenches have been dug the external walls below ground are due to have a cementitious parge coat applied to them. Before the application of this parge coat the property is not likely to reach the desired levels of airtightness in an airtest.

This delay is similar to the delay experienced on our other retrofit project,Passfield Drive where the application of the below ground insulation was delayed because of a third party. In that instance the delay was caused as a result of the gas board needing to move the gas meter.

Although these delays have been frustrating ultimately they have contributed to the knowledge that we will gain from these prototype projects. The reasons for these delays will form part of our final reports. As part of the Retrofit for the Future programme this information will be disseminated and in the future these timescales will be able to be considered when retrofit projects are programmed.

One of the LED bulbs employed through out the property. This is a Philips Ambiance Standard 12 W. Philips claim that the bulbs will last for 25,000 hours or around 25 years. The light they produce is equivalent to that of a 60 W bulb. The yellow colour adds warmth to the light emitted but is undetectable when the fitting is switched on.

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A polymer-modified cement based parge coat was applied directly to the existing face of the external walls. This created an airtight seal to the external walls and functions as a leveling coat for the application of the external insulation. The 240mm insulation boards were then cut to size and adhered to this parge coat. Thermally broken fixings were then used to mechanically fix back the insulation boards. Once the application of the insulation panels is complete a final render finish will be applied.

The application of this insulation has improved the U-Value of the wall from 1.754 W/(m²k) to 0.117 W/(m²k).

Grove Road with external insulation applied.

Rear elevation of Grove Road with external insulation applied.

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The base of the elevations will now be sealed with a parge coat to prevent draughts in this area. The airtight parge coat is a polymer-modified cement based leveling coat that is applied directly to the existing face of the external walls prior to the application of external insulation.

The airtightness layer in the attic at Grove Road is an OSB deck sealed with airtightness tape at the joints between the boards. At the eaves the airtightness layer is continued with the use of an airtight Intello membrane which is taped around the roof timbers and sealed to the parge coat on the exterior walls. There were a number of small perforations in this layer which the contractor will now seal. As mentioned in the previous post the aim is that these measures will improve the airtightness of the property to a level of one airchange an hour so that the property can reach the Enerphit Passivhaus standard. Please read more about the Enerphit standard at Passipedia the Passivhaus institute’s Passivhaus resource website:  http://passipedia.passiv.de/passipedia_en/certification/enerphit

The area to the base of the elevations due to have a cementitious airtight parge coat applied to it.

The airtightness layer in the attic. The OSB deck is sealed with airtightness tapes where the boards meet one another. The photo shows where the Intello membrane is taped to the OSB boards, externally the membrane returns down to meet the parge coat on the exterior walls. To increase insulation and to avoid interstitial condensation Kingspan boards have been inserted between the rafters at this point

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Last week BRE conducted the first airtest at Grove Road since work began on site. The test found the airtightness of the property to be 3.53 air changes an hour (ach-1). This a marked improvement on the original test in which the property was found to have an airtightness of 6 ach-1. However in order to achieve the desired Passivhaus Enerphit standard the project needs to reach an airtightness of 1ach-1. bere:architects have helped identify a number of areas for improvement with the Hounslow Homes team who are now taking the necessary actions to eliminate the remaining draughts.

It is interesting to note that if the airtightness had been calculated with standard industry methods the building would have reached an airtightness of 2.88 ach-1.

This is because the industry standard uses a volume calculation based on the entire floor area of the property. Airtightness tests on Passivhaus buildings previously used the industry standard ATTMA volume calculation but are now based upon a smaller volume, calculated from the treated floor area used in the PHPP software. Internal walls, chimneys, doors and window niches are therefore omitted from this calculation although stairwells are included. This recent change to the calculation method therefore makes it more difficult for Passivhaus buildings to achieve the same airtightness levels as previously.

Door blower fan applied to the front door as part of the airtightness test at Grove Road

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Draught prevention measures to the eaves at Grove Road

With permission recently granted to access the neighbours’ single story flat roof extension Hounslow Homes have been able to all but complete the work to achieve draught free construction in the attic.  The photo above shows the white Intello membrane, used as a draught prevention layer, taped to the rafters and sealed with Orcon F mastic to timber battens. Once the elevation has had a cementitious parge coat applied over the pebbledash finish, the draught prevention layer can then be sealed to this parge coat with mastic. This will ensure an entirely draught free construction in this area and throughout the house.

Dan Gibbons from bere:architects gives a tour of Grove Road as part of the FLASH event

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We are pleased to say that, after a long period of discussions with the neighbours at Grove Road, Hounslow Homes have been granted access over the neighbouring single storey roof. This will enable Hounslow Homes to install exterior insulation to the East elevation of the house, ensuring that there will be no gaps in the improved thermal envelope.

Next week we will be holding two visits to Grove Road as part of the FLASH programme, in association with Open City. The FLASH programme is led by the Institute for Sustainability which connects built environment Small and Medium Sized Enterprises (SME) in London with opportunities and each other with the aim of knowledge sharing about sustainability. The visits will give SMEs the opportunity to visit Grove Road and talk to bere:architects and Hounslow Homes about the work being carried out.

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The first floor bay window structure being re-constructed at Grove Road.

The installation of the Passivhaus triple glazed thermally insulated windows is almost complete at Grove Road. The old windows supported the structure of the bay, so the installation of new windows required the rebuilding of the entire bay structure. The contractors therefore waited for dry weather so that the work would not disturb the O’Donnells unduly.

As part of the work, Hounslow Homes have re-decorated the bathroom and installed an accessible bath, wash basin and WC. Completing this work early in the schedule has meant that the O’Donnells have been able to enjoy a new bathroom before the end of the project. The decoration work combined with the installation of the Passivhaus windows has left the bath room transformed. The benefits of this will be felt particularly strongly in the winter which is when the old bathroom was reportedly the coldest room in the house and was the cause of many complaints from the O’Donnells and their family.

The new accessible bath unit and newly decorated bathroom at Grove Road

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