Fig 1.  Thermal Image of Passfield Drive, East London, taken 8.30am on 31st Jan 2012.White and yellow areas show massive heat loss across the terrace. Purple shows the tea cosy effect of a Passivhaus retrofit.

At 8.30am on 31st Jan 2012 we visited our ‘towards Passivhaus’ Retrofit-for-the-Future project at 3 Passfield Drive in East London to take some thermal images of the finished retrofit. We wanted to take advantage of the cold snap that is being experienced across the country to check the thermal performance of the building.

At 8.30am on Tuesday morning the outside temperature was 1.5°C. The thermal images of the front facades of Passfield Drive, shown above in Fig 1, are a powerful visual indication of just how much energy this retrofit is saving.

In the above thermal image, 3 Passfield Drive is three houses from the left end of the terace and is clearly emitting far less heat to the atmosphere than the other buildings in the terrace. Our thermal imaging equipment enables us to read surface temperatures. The temperatures shown in the above image are the external surface temperatures at the points indicated. Six temperatures are shown on the image:

• The triple glazed Passivhaus windows of the passivhaus retrofit (minus) -0.9°C
• The external face of the insulated façade of the passivhaus retrofit (minus) -2.3°C
• A hot spot on the façade of an unimproved neighbour (No. 4) +9.0°C
• The double glazing of an unimproved neighbour (No. 4) +2.2°C.
• The un-insulated façade of No.5 +1.1°C
• The temperature of the wall near an exhaust vent at No. 6 +11.0°C

The 3.4°C temperature difference at the beginning of the day, between the façade of No.3 and No.4 demonstrates how well the 250mm of polystyrene external insulation is performing and how much more heat is being retained inside the retrofit because of it. Similarly we can see that the Passivhaus triple glazed windows installed to No.3 have excellent thermal performance and are retaining significantly more heat than the double glazing at No.4.

It would also be interesting to measure the temperatures in the evening to see if the temperature differences vary at the end of the heating day, compared to the start of the heating day.

The image below (Fig 2) is an internal image in the rear bedroom on the top floor of the house. These worrying cold bands along the top of the wall next to the loft are the result of leaving out the internal fillet of insulation (see drawing below). Over a distance of less than a metre, the wall temperature drops from over 17 degrees centigrade to just over 12 degrees. This is far from ideal and leaves a risk of condensation and mould growth which can undermine the improved warmth and healthy conditions created for the occupants by the rest of the retrofit.

Fig 2. Cold bands across the top of the external wall in the rear bedroom on the 31st of Jan 2012.

bere:architects had intended for a fillet of insulation to be installed on the internal side of the junction but this was left out due to the wishes of the building occupant. Our thermal images illustrate why it would have been beneficial to retain the fillet of insulation. Now that the occupants understand how even a small cold bridge can affect their thermal comfort, the residents want the fillet put in, but the contract works have finished and it may not be possible to find funding to do the intended work at this late stage.

The foundations at 3 Passfield Drive have had external insulation applied to a depth of 1m below ground level, so there is no significant heat loss. However there is a significant amount of heat leaking through the foundations of the adjacent houses (right hand side of Fig 4). The heat is leaching across the front of the retrofitted building but reduces out of view to the left of the picture, further away from the neighbouring house which is the source of the problem.

Fig 3. The un-insulated house (right) is losing a substantial amount of heat through its ground floor

Fig 4. Turning to the left, the effect of the neighbour’s ground slab heat losses diminishes

In spite of the defective insulation on the top floor, Mr Muhammad tells us that the house is much warmer after the retrofit than before, and more comfortable, and much cheaper to heat. Before the retrofit, the family could not sit for long on the ground floor in the winter months because of the cold temperatures and draughts. Now the family has much higher indoor temperatures and at the same time winter fuel bills have halved. We will shortly be producing a full report of the fuel cost savings.

Mr Muhammad spoke of how in winter, prior to the retrofit, it would take two hours for the house to warm up in the mornings. Now with his wife and son’s family away visiting their sick grandmother, he needs to put the heating on for ten minutes every couple days. When his wife and family are home, the heat from the cooking itself is usually enough to heat the house.

Even with the defects that we have highlighted the building is performing very well while many of the neighbours will be using a lot more heat in their struggle to keep warm during the cold weather.

Un-insulated houses are problematic for the following reasons:

• Unchecked fuel poverty is inhumane and affects the health of vulnerable people, especially the elderly.
• Illness caused by cold homes costs the Health service large sums of money.
• Money wasted in heating houses goes overseas, draining the national economy.

There is clearly a political opportunity to spend some money now in order to save money in the longer run. In a time of austerity, this is a very significant opportunity to save the economy while saving jobs and saving money.

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Passfield Drive showing No 3 in the centre of the picture with lighter coloured render over the external insulation.

On a recent visit to Passfield Drive the house was noticeably warmer than it was at this time last year.  On the visit the Muhammads said that they have not yet needed to put any heating on.  Mr Muhammad noted that the Bangladeshi meals which Mrs Muhammad prepares at least once daily are enough to keep the house warm throughout the day. This clearly shows that the Muhammads are already benefitting from the Passivhaus energy saving measures employed in the retrofit.

Previous to the retrofit the Muhammads would have opened windows to expel the steam that the frequent cooking produces. With Heat Recovery Ventilation (HRV) in place the Muhammad’s are now able to expel this steam and smells from the cooking without losing valuable heat. The HRV unit has an easy to activate boost function which can be turned on for short periods whilst cooking.  The HRV system has the added benefit of being a lot quieter than most cooker hoods.

Temperature monitors within the house show that internal temperatures are remaining at around 22°C throughout the day and night. From the perspective of comfort this is good but it is surprising as we would not expect the temperatures to remain this warm throughout the night.  We are in the process of further analysing the monitoring data of the solar thermal system and will post more information here at a later date. We are also looking forward to soon being able to access gas, electricity and water monitoring data. Having access to this data will increase our understanding of the energy use of the post retrofit property.

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Mr Muhammad and his two sons outside the completed property

We have now reached practical completion at Passfield Drive and last week we carried out a softlandings event to fully hand the project over to the Muhammads. The Muhammads were kind enough to invite representatives from bere:architects, Southern Housing and AD Enviro to lunch for this event and we enjoyed an impressive and delicious traditional Bangladeshi meal. Some of the food was cooked on the new barbeque which Mr Muhammad has made out of the old water tank which became redundant when the Solar Thermal system was installed.

The Muhammads expressed great appreciation for the retrofit work that has been carried out on their house. Interestingly they have yet to experience the cost savings associated with a Passivhaus approach because their recent bills reflect the cost of the energy used by the contractors whilst they were on site. However we would expect to see a marked reduction in their next gas bill as at this time of year the Solar Thermal will be producing the majority of the hot water. The cost savings of this retrofit will become more apparent in the Muhammads winter gas heating bill which will be reduced by 80-90%. However the Muhammads are appreciating the other benefits of a Passivhaus approach. At this time of year this is most apparent in the internal temperature being cooler than the external temperature, a product of the external insulation, draught free construction and triple glazed Passivhaus windows. The triple glazing will also ensure a reduction in sound levels of any disturbing noise from outside. We were pleased to hear that although the construction work did present difficulties at times the Muhmmads are in no doubt that the finished project was worth it.

As part of the Softlandings event Dan Gibbons from bere:architects explained the heating and cooling strategy of the house which employs a Heat Recovery Ventilation Unit throughout the year and windows for summer cooling. Dan also explained the Solar Thermal system and the Muhammads were given the opportunity to ask questions about the technologies and overall approach to the retrofit.

As well as being a great way to get feedback about the project an effective handover or Softlandings was a crucial part of making this project a success and ensuring that the Muhammads enjoy the full benefits of the energy saving technologies that have been employed at Passfield Drive. As part of every Softlanding bere:architect’s produce a simple visual user guide for the residents.

Click here to view Passfield Drive’s Softlanding user guide.

This project is, however, not over yet. News of resident interviews post completion and the finding of monitoring data will be posted here in the future. Also expect to see a second and third episode of our Retrofits for the Future video documentary on the project posted here. If you have not seen the first episode of this documentary please watch this at http://bere.co.uk/films.

Team members from the project enjoy lunch at the Muhammads

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The monitoring and smart metering includes monitoring of internal and external temperature, internal CO2 and relative humidity and the Solar Thermal system. The data will be transmitted by radio to a central hub which will enable the data to be viewed on line.

bere:architects recently had a preview of the readings from these monitors. The readings highlighted some initial problems with the monitoring equipment which have now been rectified. However the readings from the solar light meter or Pyranometer are still not accurate. The contractor is currently working to rectify this.

The temperature sensors have shown that over the last five days the internal temperatures have remained between 22C and 24C throughout the day and night with external temperatures varying between 14C and 27C.

Passfield Drive with new timber canopy installed.

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The front elevation of Passfield Drive near completion with Mr Muhammad’s newly planted fennel plants in the foreground

The external works are nearing completion at Passfield Drive. To the rear of the property the final lengths of larch cladding and the single ply roofing membrane have been installed to the extension.  The original paving slabs which were removed and set aside have been reinstated in the front and rear gardens.

This week the Muhammad family received a pleasant surprise when the contractor installed a water butt in the rear garden. This was not included in the original proposals for the project but was added as an extra water saving feature. Mrs Muhammad was particularly happy as the Muhammads grow their own vegetables and she had planned to purchase a water butt herself this summer for use in the garden.

We are yet to conduct a formal handover interview with the family. From our conversations with them on site we understand that they are already appreciating the improvements to the windows and whole house ventilation and thanks to the external insulation are now enjoying a cool house in the unusually hot weather.

The new Rain Water Collection Butt positioned next to the new Larch clad extension.

The rear elevation at Passfield Drive showing the works to the Passivhaus standard extension are complete. This new timber frame extension is clad in European larch, uses Passivhaus certified triple glazed windows and is insulated with 375mm of wood fibre insulation in the walls and 225mm of mineral wool combined with 150mm of wood fibre insulation in the roof.

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The door fan fitted to the front door at Passfield Drive pressurises and depressurises the house to establish an average value for air infiltration.

Last week a third airtest was conducted at Passfield Drive. This was the final airtest with the contractors on site (BSRIA will be completing independent tests following completion of the works). The result was 1.9 air changes per hour at 50 pascals (ach-1) or an air permeability of 1.4m3/hr/m2. This was an improvement from the previous airtests and demonstrates that the Passivhaus approach we have taken has made a very significant reduction to the draughts within the building. In the original airtest prior to the retrofit the air permeability was found to be 6m3/hr/m2 at 50 pascals

Our knowledge of Passivhaus design has enabled us to create a draught free front facade, rear façade, ground floor and attic floor at Passfield Drive. Whilst the property is now five times more draught free than required under building regulations and can therefore be described as very draught free the airtest has shown that there is slightly too much air leakage under pressure to achieve the airtightness required for a certified Passivhaus retrofit building. These few remaining draughts are likely to be due to the fact that the building is part of a terrace with floor joists and structural timbers penetrating into and potentially through the party walls; allowing air to pass through to the neighbouring houses.

In order to eliminate these draughts completely it would be necessary to take up the floor boards on each floor and seal around the penetrations, work which is unfortunately too disruptive in an occupied building. We have assessed the impact of the airtest result on the predicted energy consumption of the house using our Passivhaus Planning Package (PHPP) analysis. The increase in air leakage from the predicted 1 ach-1 to 1.9 ach-1 increases the specific heat energy demand from 22 kWh/(m2a)  to 25 kWh/(m2a). This nevertheless still represents a reduction in specific heat energy demand of 91.75% and a reduction of specific primary energy demand of 79% as compared to the pre-retrofit building.

We have concluded from this airtest result that the most reliable way to achieve Passivhaus levels of air tightness the necessary levels of energy reduction required to achieve government CO2 targets is to retrofit an entire terrace at the same time. By applying our retrofit approach to an entire terrace it would be possible to ensure each building within the terrace could achieve the requisite levels of air tightness. Combined with high levels of insulation, triple glazed windows and heat recovery ventilation, as demonstrated at Passfield drive, and the reductions in energy consumption would be expected to be as much as 85-95%.

By retrofitting a whole terrace at a time the projects would also gain from economies of scale. This would apply especially to heat recovery ventilation (HRV) which could be implemented by using one HRV unit to ventilate an entire terrace, producing energy efficiencies and cost reductions. Externally insulating as we have done at Passfield Drive would of course also bring much needed visual benefits to old building stock.

Paul Jennings of ATTMA seals the heat recovery duct work during the airtest.

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Vacupor is a vacuum foil insulation which has very low thermal conductivity enabling us to achieve a low U – Value in the floor whilst only adding 25mm to the height of the floor.

The manufacturers state that Vacupor has a thermal conductivity of 0,005 W / (m×K).

Because the thermal performance of the insulation is reliant on the vacuum inside the panels it is vital that the insulation is not perforated, if a panel is perforated that panel no longer contains a vacuum and its thermal resistance is greatly reduced. To protect against this a protective layer must be laid above and below the insulation. To avoid thermal bridges in gaps between panels the insulation is manufactured to fit the floor area exactly

Vacupor insulation being laid with a 3mm protective layer of foam beneath

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The north elevation, with parge coated applied, ready for the application of external insulation.

The parge coat for the external insulation has been applied at Passfield Drive and application of the external insulation has commenced. The grey parge coat is a Polymer-modified cement based leveling coat and is applied directly to the existing face of the external walls prior to the external insulation to ensure that no draughts penetrate the envelope of the building.  The graphitized, ‘grey bead’ Expanded Polystyrene (EPS) is adhered directly to this parge coat. Sub-contractors were due to start the application of the external insulation on site on Wednesday but have not been able to make it to site until today (Friday).

The 250mm and 200mm EPS, being applied to the front and back of the property respectively, will substantially improve the U-Values of the walls and eliminate cold bridges. Insulating in this way also has the advantage of decreasing the energy requirements of the building without reducing the internal floor area or creating potentially damaging moisture build up in the walls. bere:architects believe that external insulation is the key to the future of low energy retrofits because it can be applied on homes throughout the country in large numbers with minimal disturbance to the building.

The first pieces of external insulation are adhered to the parge coat.

Before this insulation was applied bere:architects installed a temperature probe into the foundations of the house. The readings from this probe will enable us to compare the temperature of the soil beneath the house and the effect of the external insulation to the foundations.

The 300mm probe was inserted into a predrilled hole and penetrates in to the soil underneath the building

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3 Passfield Drive before work began on the retrofit

bere:architects have been producing a video documentary about their  Retrofit for the Future projects.

Please watch the first episode of the Retrofits for the Future video documentary at:

http://www.youtube.com/watch?v=xiAp17uwP2c

Please visit bere:architects other retrofitdiaries.org blog at:

http://hounslowpassivhausretrofit.retrofitdiaries.org

www.bere.co.uk

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Plywood linings are installed to the reveals around the Passivhaus certified triple glazed windows and have been given an initial coat of paint.

We are nearing practical completion at Passfield Drive, the works are now due to be completeted at the end of May. Work to the second floor bathroom is complete, window linings are near completion, the kitchen is being installed next week and the final coat of the external insulation render system was applied today.

The Muhammads have been accomodating to the contractors and all those who have visited the site throughout the construction works. However for some periods the disruption that is always associated with internal building works has meant that the family have not always found the project easy to live with.

With practical completion approaching, and the new windows and external insulation making a striking visual improvement to the house, the Muhammads are excited by the concluding phase of the work.

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