Interim certificates confirm site on course for Code 4

All the units on the site have been issued with their design stage Interim certificates under the Code for Sustainable Homes (May 2009) and are on course to get their final certificates once complete.

The Code 4 pass mark of 68 percent has been comfortably exceeded with dwellings scoring between 72 and 77 percent. Although not outstanding in itself these results are particularly pleasing given that there are tensions between the Code and Passivhaus that make some credits harder to achieve.

These areas include:

• Secured by design (Man 4) – although Passivhaus windows and doors (Internorm Edition are being used at Wimbish) have excellent locking mechanisms they do not have the SBD approvals that is often required by police Architectural Liaison Officers.

• Global Warming Potential of insulation (Pol 1) – nearly all insulation used on the site has a GWP of less than 5 but the German Passivhaus loft hatch supplier was unable to provide any evidence of this. Consequently the credit could not be achieved.
• Responsible resourcing of materials (Mat 2 and 3) – many of the materials were sourced from suppliers where the necessary certification could not be guaranteed and so the Code strategy set early in the project was to not pursue these credits. It is likely that a number of credits could have been achieved if necessary. More ‘Code compliant’ products could have been used but these often do not have the certification required for Passivhaus.

• Energy and Carbon (Ene1) – a gas heated Passivhaus should achieve a good score in this area but there are a number reasons why this is not the case. Firstly there is a well recognised problem in the Code with flats and mid terraces whereby the small amount of external surfaces makes it hard to show significant carbon reductions through insulation measures. The flats only narrowly achieved the necessary 44% reduction in carbon emissions (block average). PV could have been added if really necessary for Code compliance but this would not have helped Passivhaus performance since it focuses on rewarding demand reduction. Thirdly the non-standard (for the UK) heating strategy of a thermal store supplying a wet heating coil in the MVHR supply air duct cannot easily be entered in the SAP calculation making it hard for the likely carbon reductions to be recognised in the calculations.

These issues will all be resolved in time as the supply chain recognises the importance of both sets of certification. More products and UK suppliers in particular will all help to push down the cost of achieving Passivhaus in the UK.

Nick Jones, Associate Director, Inbuilt

Site Visits Extended! Plus, FAQs

Due to overwhelming demand the project team have decided to facilitate an additional open event day at the Passivhaus site in Wimbish in February. The open event will provide a brief presentation followed by a walk around the site. Time for questions and answers will be at the end. The event is free but restricted to 15 attendees and a maximum of 2 people per organisation. The event booking is on a first come first serve basis. For enquiries and bookings please contact umaccariello@hastoe.com

Upcoming Events

Tuesday 4 January 2011 – FULLY BOOKED

Tuesday 1st February 2011, 1.30pm to 4pm

The open events we held in November and December were really well attended and even though we had a few late cancellations due to the snowy weather condition in early December we were able to fill most spaces at the last moment.

Nick Jones of Inbuilt and Chris Parsons of Parsons & Whittley are doing a fantastic job with their presentations. They provide an interesting and informative overview of the Passivhaus principles and provide some specific examples in regards to Wimbish. The December site walk around was rather brief due to the freezing conditions and everybody appreciated the hot cup of tea or coffee back at the village hall.

The discussions back at the village hall provide a great opportunity to get further valid information and here are just some of the frequently asked questions:

Q:   What are the cost implications in comparison to a conventional building?

A:   Hastoe’s cost consultant Davis Langdon is currently undertaking a cost comparison to some of Hastoe’s Code Level 4 schemes and this information will be available on the blog soon

Q:   What happens if people want to fix items like pictures or shelves to the walls?

A:   Fixing to internal walls is not a problem as long as the occupants fill the wholes with a wall plug and screw. Hastoe will need to ensure that following any tenancy change wholes left will be filled to re-instate the airtightness of the building.

Q:   You have explained that the construction method at Wimbish is thin joint blockwork with an external insulation and render finish. This sounds like a standard construction method used in England?

A:   The approach for Wimbish was to use local materials where possible and local labour, and it is indeed correct that this method is not ground breaking and is widely used, but the standards for a Passivhaus do need to be to a much higher.

Ulrike Maccariello, Development Manager, Hastoe

Arctic weather slows progress

I've been anxiously hoping to add something to the blog of value over the last month, but frankly the weather has beaten us all and I think it's unlikely to relent before Christmas. Our last site presentation included only a restricted walk round the site because so much of the site and scaffold was frozen and icy. Hopefully the visits and presentations have been informative, we certainly get some good feedback. See other blog entries for more details on these.

The blocks are now all complete in terms of superstructures, and felt and batten is halfway there but the weather has even held that up!

Windows have arrived and everyone is very excited by the quality of the product, even though they still sit securely in the container. Given that they are already triple glazed, they are quite heavy, (hence the debate regarding fixings), and manouvering them on an icy site may be problematic.

The external insulation has also arrived so we really just need the weather to clear and we can get progress moving again.

It looks like we have secured a great monitoring arrangement with the UEA and we shall be installing some telemetry in one of each of the different units to provide feedback on the energy use of the properties, hopefully over a two year period.

In the meantime, Happy Christmas to all our readers and we look forward to reporting real progress in the new year!

Chris Parsons
Parsons + Whittley

All Trussed Up

The whole team rolled up their sleeves to help the adjacent village hall recently by re-decorating the outside of the hall as a thank you for their patience whilst we disrupt their car park and access. Luckily the sun shone, and the brilliant white paint caused several instances of reflected sunburn! There should be some photos on the gallery page.

The build is proceeding well, with the roof trusses going on to plots 1 - 6 and 11 - 14. Plots 7 - 10 will shortly follow. The large overhang on the eaves required for additional shading has been designed in two parts to break up the mass a little and there has been some discussion on site regarding the best fixing methods, but that is all now pressing ahead. We are wondering whether to fit some of the eaves insulation during the roofing process to ensure a quality fit and to make sure there are no gaps.

We had the first of a series of open meetings to show interested parties around on Tuesday, (2nd Nov), and the contractor kindly laid on guided tours after we (Parsons + Whittley) and Inbuilt had given presentations in the village hall on the principals of Passivhaus and their interpretation at Wimbish.

The windows should be arriving soon, and when these are fitted we plan an early pressure test to see how we are doing. You wouldn't believe the discussion around the window fixing detail, although for those who have built Passiv before, you probably would! The remaining membranes, tapes and grommets all need to be fixed pre-plaster so that we can detect any weak spots in the strategy.

Weekly design meetings on the site are helping to resolve issues before they arise, although the tea and biscuit supply to these meetings is taking far too low a priority in my view.

Chris Parsons
Parsons + Whittley Architects

UK Passivhaus Open Days

The Wimbish Passivhaus development will be open on Friday 12^th November as part of the first ever UK Passivhaus Open Days.

The construction site will be open for pre-booked visits at the following times: 11am, 12noon, 2pm and 3pm.

Advance booking only through Jane Barnes Jane.Barnes@davislangdon.com

Visitors will need to bring their own safety equipment (boots and hard hats).

Up to floor joist

As it took a while to get the website and blog up and running, my first blog comes as we await the first floor PC slabs for the flats.  For historical purposes, 400mm of Dow Floormate was placed without difficulty beneath the 300mm RC rafts, and the insulation is now all nicely wrapped up and backfilled. All the service penetrations were installed ready to receive air tight grommets and the blockwork commenced.

Most Passivhaus’s in the UK are built by enthusiasts for enthusiasts, but at Wimbish we are trying to build them in a normal commercial volume house building environment. That means getting your everyday subcontractor to understand the process and the importance of quality and detailing that wouldn’t normally apply in this environment.

Initially this included making sure the Aircrete thin joint blockwork was laid fair face to the outside rather than the inside, as the insulation has to be fitted later with no air gaps between the sheets.

Our air tightness barrier is to be the wet plaster but where we pass through the first floor void the ground and first floor plaster skins are linked by a Solitex Plus airtight membrane. Initially we had proposed PC slabs even in the houses because of the ease of obtaining this air tight seal, but value engineering changed this to timber posi-joists which present a few more challenges, particularly with restraint straps and in the corners. Several mock ups and some significant time and effort on site has been expended to ensure this is properly placed and installed.

So, the PC slabs should arrive on Monday for the 6 flats and then we can speed ahead to getting the roof trusses on. The next passivhaus task will be the air tight membranes at ceiling level, and then maybe a preliminary air test before plaster to see how we are doing.

Chris Parsons

Parsons + Whittley Architects

17^th October 2010

Site Visit Opportunity

Hastoe Housing Association in conjunction with the project team are facilitating a series of open events at the Wimbish Passivhaus site. The open events will provide a brief presentation followed by a walk around the site. Time for questions and answers will be at the end. The events are free but restricted to 15 attendees per event and a maximum of 2 people per organisation. The event bookings are on a first come first serve basis. For enquiries and bookings please contact umaccariello@hastoe.com

Upcoming events:
Tuesday 2 November 1.30pm to 3pm
Tuesday 7 December 1.30pm to 3pm
Tuesday 4 January 1.30pm to 3pm

Ulrike Maccariello, Development Manager, Hastoe