Wednesday, 7 December 2011

Blog Assignment no. 2 - Passive House construction in Carlow


The construction of this farmhouse style building commenced in 2010 in Tullow, Co.Carlow. The house was featured on RTE's program About the house on November 29th 2011 .
First and foremost, the clients wanted a beautifully designed home and if possible, that it be built to a passive standard to achieve low energy costs and avoid dependence on fossil fuels in the future.

House Details

The house plan ( 298m2 floor area) was U shaped with traditional farmhouse features. The client's preference was blockwork construction as they felt the area was windswept and open and that blockwork gave them better solidity than timber framed construction.

The foundation: On top of concrete ground beams, 400mm of insulation was laid under the concrete raft foundation. This separation of the wall from the ground eliminated thermal bridges.

The external walls: The external wall was made up of outer and inner blockwork leafs with a 300mm cavity. This cavity was filled with bonded polystyrene bead insulation. The outer blockwork received a breathable render while internally, an air tight plaster with a service cavity filled with insulation avoided the thermal envelope being disturbed. The wall ties were made from basalt as it has a low thermal conductivity. The U value achieved for the wall was 0.1W/m2K.

The windows: A-Rated passive standard windows including three seals on the window frame were used. Plywood boxes were attached to the internal blockwork allowing the windows to sit in the cavity area, which is the optimum position for a window in a passive house.

Air tightness: This was achieved by attaching an air tight membrane to the ceilings which formed a sealed envelope with plastered internal walls and floors. The passive standard three seal windows and attention to air tightness at joints around windows and doors meant that the result from the blower door test was 0.25 airchanges per hour which is well below the maximum level for certification of 0.6.
Below is a video of a typical blower door test.


There were several delays on the project - The MHRV system design initially wasn't certified, the harsh winter of 2010 meant construction came to a standstill and then the builder ceased trading. Building with a timber frame method of construction would have sped things up somewhat as components can be prefabricated (e.g. wall sections) and erected even in very cold weather.

I thought it was interesting to note that the MHRV system was installed after the blower door test and that there was no air test done on the pipework afterwards (the program didn't say this anyway). In our talk from David McHugh from pro air he told me that they usually expose the pipework to the blower door test to check for any leaks.

Other interesting information from the program was given by Jeff Colley of Construct Ireland (the only magazine dedicated to sustainable construction in Ireland).  He informed the viewers that:
  • FAS have commenced the world's first passive house training course for craftsmen
  • Ireland has the third highest number of certified passive house designers in the world
I think that this is some good publicity at last for the construction industry here instead of the culture we saw between 2000 and 2006, where the emphasis was on quantity and speed with quality losing out.


The client's are currently trying to complete the project by direct labour and have managed to maintain continuity in terms of craftsmen. The house is only nearing the end of its construction due to the delays that I mentioned earlier but I would be surprised after seeing the attention to detail in the construction methods if the house is not certified to a passive standard.

Monday, 14 November 2011

Assignment no. 1 - Passive Houses: Achievable concepts for low CO2 housing

This paper, entitled " Passive Houses : Achievable concepts for low CO2 housing" was written in January 2006 by Henk. F. Kaan and Bart J. de Boer of the  Energy research centre of the Netherlands. The paper was presented at the ISES conference 2005, Orlando, USA in September 2005.
In January 2005, an EU supported project (involving nine countries) called Promotion of European Passive house(PEP) commenced to promote passive house development based on the German/Austrian model. This paper examines the issues that the PEP project relates to. 
The main points of the paper are:
  • There is a need for more energy efficient buildings because "in the Western world, 40% of all energy consumption is from building".
  • Germany and Austria are the front runners in passive house construction with over 5,000 passive houses  built to date and more to follow.
  • Some European countries are introducing passive house initiatives but shouldn't just copy the German/Austrian model. Climate, building tradition, specific building codes and building details differ from country to country and this affects design and construction.The economics of passive house building vary from country to country.
  • The PEP project must define the term Passive House for each country. The writers inform us that "The energy use in an absolute sense does not by definition tell whether the building is good or not". One must question that achieving a passive house shouldn't in all cases be based on energy usage of 15KWh/m2 but based on different criteria for different countries. For instance in warmer countries in southern Europe, shouldn't energy required for cooling be taken into account?
  • The behaviour of occupants is also a huge factor once the house is built. For example, mis-use of the heating and ventilation system leads to over use of energy. The writers ask should the passive house technology "take over the decisions?" and systems be designed as "fool proof". 
  • While solar energy is important, it is the overall combination of the heating elements in the building that contribute to satisfactory indoor comfort. These heating elements include: air tightness, heat recovery from ventilated air, insulation building type and shape. These elements were found to be the most important when the energy research centre of the Netherlands used the computer program "TRNSYS" to carry out a study on optimum use of solar energy in building.
The paper concludes by the writers assuming that every country has different characteristics. The PEP hopes to look at all the countries involved and find similarities and differences "and show how the countries can learn from each other."
I agree  that every country has different characteristics such as climate, building traditions, access to building materials and passive houses should be defined differently in different regions.
 Also, in countries where the concept of passive house is in the early stages, it is more difficult to obtain the relevant building materials. These may have to be imported and one then has to consider the carbon footprint disadvantage and cost of the passive house option.

Note: Click on this link to go to the PEP website for more information:

Note: Here is a visual presentation showing the basic principles of  Passive House construction

Tuesday, 18 October 2011

What can be a passive house in your region with your climate?

Dr. Wolfgang Feist tells us that specific Passive House solutions must be adapted for each region and climate. He says the "Passive house method" can be used to design buildingd to suit there location and climate. The peak heating load of 10w/m2 is critical to the the energy efficiency of the building. Once the peak heating load is less than this, the ventilation system can be used for space heating and a separate heating system is no longer required. Other methods for finding a passive house solution are 1) technologies such as insulation, shading, high efficiency appliances 2) use a heat recovery ventilation system. It is important to keep comfort at a high level, control affordability, use insulation, use shading in all climates with high levels of radiation, ventilators in HRVS should be highly efficient, the ground could be used as a heat or cold buffer.
The Parametric Study method checks for energy demands, financial investment and healthy indoor climate. The Parametric study is performed using a computerised thermal building model. Using this model the Passive House Institute can successfully develop solutions for varying climates.

Above is a video of a  passive house built in Galway with its owners and builder describing it