Wednesday, March 2, 2011

Refurbishing Irish Houses to Passive Standard Case Study in Wicklow, Ireland

The Passive House Popularity
Society has recently developed a growing consciousness of the need for energy efficiency for cost savings, sustainability and environmental protection. The passive house construction method delivers massive energy reductions ticking all boxes.
The passive method reduces home energy costs such that heating systems can be virtually eliminated through key considerations. Currently, there are over 25,000 units constructed in the EU and it’s spreading worldwide.

Contribution to Energy Demand in Ireland
While a welcome evolution in building standards the majority of the 1,500,000 houses in Ireland are massively energy inefficient while less than 1000 A rated (low energy homes) were registered in Jan 2011. Compared to the 2005 building regulations the passive standard is 80% less energy intensive and 94% more airtight. 

Arguably with minimal demand for new houses the passive standard is unlikely to contribute to national energy demand reduction for the foreseeable future. But recent refurbishment projects have shown that passive standards can be successfully applied to current stock giving them a new future proof lease of life. 
Case Study: Glencullen, County Wicklow, Ireland
Viking House is undertaking a retrofit of a 1960’s bungalow consisting of a 300mm thick cavity wall, strip foundations, and standard pitched roof construction. This is typical of current housing stock in Ireland, particularly those with a BER E rating or less. While the build consisted of a passive house standard extension we will focus on the existing section of the house for the purposes of this article.

Key Components
The 15 kWh/m2 heating demand for the passive standard was achieved by:
·         External wall -improved to U=0.11W/(m²K). 100mm cavity filled with EPS bead insulation plus 200mm of EPS external wall EPS insulation. 
·         Floor -improved to U=0.08W/(m²K). 400mm polystyrene, wooden floor
·         Roof -improved to U=0.11W/(m²K).  300mm cellulose insulation.
·         Windows –new triple glazed units U=0.08W/(m²K)
·         Heat Recovery Unit

Thermal bridging was a particular issue at the junction of the external wall and the floor as shown in the PHPP (Passive House Planning Package) graphic below.
The solution wa to extend the insulation 500mm below finished floor level (FFL) externally and 300mm in the cavity as per the next PHPP graphic.

As you can see the thermal bridge is minimized with the surface temperature now at 15.5°C which will eliminate condensation and add thermal comfort.  Note: as damp proof course was 300mm below FFL the issue became much simpler to resolve.

Other Applications

In the UK a number of social housing projects are being undertaken to the passive house standard.

Potential Problems with Residential Passive Retrofit

·    Achieving Optimal Orientation & Internal Layout for Solar Gains
·    Overcome orientation issues by adding extensions in right orientation
·    Solid floors and walls : insufficient insulation &  excess thermal bridging
·    Services passing through building envelope
Best Case Scenario for Passive Retrofit

·     Cavity wall & suspended floor construction. 
·     At least one major wall facing south.
·     Space to extend laterally and vertically if required (for solar gains etc).

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