For my case study of an international, certified Passive House, I have chosen the the Denby Dale Passive House in West Yorkshire in England. This Passive House was constructed by Green Building Store's construction division; Green Building Company for clients Geoff and Kate Tunstall. The Denby Dale Passive House is the first certified Passive House in the UK to be built using traditional cavity wall construction. The house has pioneered the combination of traditional construction methods with the German low energy Passive House design methodology.
Costs:
The Denby Dale house is a 118m2 three-bed detached house with basic build costs of approximately €165,000. Not included in this initial cost were: garage, any external works, service connections, decorating, and any sun shading work.
Design:
The Tunstalls had initially wanted a rectangular shaped home but this design did not perform to the Passive House standards after modelling with Passivhaus Planning Package (PHPP) software. Instead a rectangular shape was chosen with the longest side facing south so as to achieve optimum solar gains. This new design met the desired 15 kWh/m2/annum level required for space heating. The clients also expressed there desire to have a conservatory in there new house. This is often a problem for passive houses as it is very hard to retain heat within conservatories, however this conservatory was incorporated into the building envelope as an integral solar space, with exterior brise soleil put in place to minimise overheating.
Insulation:
As heat retention was one of the primary aims of this development, the type of insulation used would be vital. In the end 100mm mineral wool batts were installed in the cavity three deep. This results in 300mm of insulation with each layer having a lambda value of 0.037. The outside of the cavity wall comprises of 100mm natural stone, with the inside comprising of 100mm block work. The Denby Dale house also uses a 500mm fibreglass quilt in the roof void and 225mm of high-performing poly foam insulation in the floor.
Heating:
This house requires at least 90% less heating than the average UK house. The peak heating load for this house is calculated in PHPP as being 10W/m2 when the outside temperature is -10ºC. To allow for this space heating is provided by a conventional condensing gas combination boiler. Water heating is provided by solar panels, which were accquired under a local grant.
Points of interest:
- Walls in the Denby Dale House have a U value of 0.1 W/m²K.
- The Ecopassiv timber windows that were used in the build are triple glazed with low-emissivity coatings and argon fill and have a whole-window U-value of just under 0.8W/m2K (and glazing U-value of 0.6W/m2K)
The Denby Dale house overshot the airtightness requirement (0.6 air changes /hour @50Pa) by about 33% and also came in well under the space heating requirement of 15 kWh/m²/annum.
Hey David this is an interesting case study for a passive house you hav chosen as it uses traditional cavity wall construction. Seeing as this project was deemed a succes is there any reason why this construction method isnt used for all passive house projects in the UK & Ireland or was this method chosen for a specific reason?
ReplyDeleteHey!
ReplyDeleteYes this Passive House was a success. Cavity wall construction was chosen for 3 reasons...
1.Cavity walls contribute to a high thermal mass within the insulated building envelope.
2. The company that was appointed to oversee the construction of this house (Green Building Company) are only just moving into this area of construction (Passive House) and they were most familiar with cavity wall construction from previous projects so they decided to use this method of construction on this build. Also by choosing this method of construction most of the materials could be found in the local hardware store.
3. West Yorkshire planning rules require natural stone facing on the exterior of new buildings and so this ruled out the option of block-built construction with rendered finishes.
There is no reason why the cavity wall method of construction cannot be used in Passive House builds throughout the UK & Ireland. In my opinion cavity wall Passive Houses are the best option in Ireland and the UK due to there high thermal performance in the climate we experierience and as it is the most common form of construction used there is no need for specialist contractors.
Hi Dave. The heating requirement is said to be below the 15kWh/m²/annum requirement. Is there any data available as to the actual performance of the house given its Northern England location. Also if a gas combi boiler (i assume room sealed) were there tricky plumbing issues with regard to the boiler heating water on demand rather than coming from the thermal store heated by the solar panels?
ReplyDeleteHi Dave just in relation to what Cyril was saying today about staying away from gas altogether as it leads to many problems, do you think it was a good idea that they have installed a gas combi boiler??
ReplyDeleteHey Sean, good questions.
ReplyDelete1. The peak heating load for the Denby Dale house was calculated in PHPP as being 10W/m2 when the outside temperature is -10ºC. The house has a total floor area of 118m2 so the total heat demand was calculated to be 1.18kW. Upon certification the space heating was recorded at 15 kWh/m2/annum however as stated it was more than likely lower than this but the certification process only verifies final PHPP figures as meeting Passivhaus standard of 15 kWh/m2/annum.
2. The system boiler, also known as a sealed system boiler was purchased from Vaillant: The Eco TEC 612 has an integral expansion vessel so there was no need to interrupt the airtightness barrier with an attic space header tank. The space heating system consists of:
•A duct heater installed in the supply side duct of the MVHR system- to heat the ventilation supply air
•One radiator in the living room
•Two towel rails
Those four heating items added together deliver more than the 1.18kW of space heating needed, but because present gas boilers aren't made to run at such a low output there was a need to have an adequate volume of water within the system, so the capacity had to be made larger than is actually needed. This resulted in an unavoidable extra cost.
The client was adamant that most of their budget be spent on the building fabric, rather than build something bristling with expensive renewable such as solar panels and wind turbines that years down the line may require structural changes. The heating system can always be changed but the way a building has been constructed cannot.
ReplyDeleteThe client chose a gas-combi boiler as the gas network runs past the house and because gas boilers are cheap, readily available and easy to maintain, with minimal maintenance costs.
However mid-way through the project a grant became available to the client to install solar panels. They decided to install the panels but this meant changing from a combi boiler to a much more sophisticated system boiler. As stated in Sean’s response this resulted in extra costs but it should help to keep the gas bill down.
It was probably a good idea in the long run to install the panels during construction as you could cause all sorts of air tightness issues later trying to retrofit install solar panels. Room sealed should be OK for gas in terms risk of gas fumes especially in such an airtight house. Extract ventilation should also keep the air fresh but I personally would not risk a gas appliance in a passive house.
ReplyDeleteYeh I agree with your last point, as for installing the solar panels during construction it was just a case of poor organisation by the client.
ReplyDeletessir_passive, I cant understand why gas in a Passive House should present any problem whatsoever (apart from it operating at less than 10% design load). Passive house with MHRV delivers 100% fresh air continuously - air quality inside a passive house is typically BETTER than it is outside in the garden - there is zero re-circulation of air so zero chance of breathing in the products of gas combustion. You can't say the same about a naturally ventilated code-compliant dwelling.
ReplyDelete