Fin MacDonald

Last week our Ireland project wrapped up and we submitted our final report and did a presentation to students at I.T. Carlow in Ireland with our findings. Our group consisted of:

• Myself
• Karyn Brown from Holland College in PEI
• Deirdre Cahill from I.T. Carlow in Ireland

The project was to develop a retrofit plan to upgrade and existing Irish home to meet the PassivHaus standards. Our group did an excellent job. Just to recap, the PassivHaus standards require:

Heating: 15 kWh/m² each year
– or –
Peak Load: 10 W/m²
– and –
Total primary energy use: 120 kWh/m² each year
– and –
Air tightness less that 0.6 air changes per hour at 50 pascals
– and –
No thermal bridges (The co-efficient of heat transfer needs to be below a certain value)

The real challenge was meeting the heating load. The building was not orientated in a way that it could benefit from passive solar gain from the sun. It had west/east facing front/back/roof. The building had a heating load of 121 kWh/m2, and we needed to reduce this to 15 kWh/m2. We accomplished this with the following upgrades to the building:

1. 200 mm of rigid polystyrene insulation was added to the exterior of the home
2. 60 mm of polystyrene beads were pumped into the cavity of the wall
3. All windows were replaced with triple glazed PassivHaus windows with a U-value of 0.58 W/m2*C
4. All doors were replaced with PassivHaus certified does with a U-value of 0.58 W/m2*C
5. 200 mm of rigid polystyrene insulation was added to the attic
6. An air barrier was added to reduce air infiltration

Once the envelope was upgraded to meet the 15 kWh/m2 requirement the home also met the 120 kWh/m2 total energy use requirement. This is because the occupants didn’t use very much energy at all for appliances. This was discovered through analysis of the energy bills.

The payback for the upgrades was not very favorable. It required over 30 years to reach equity payback, and in the 50 years remaining in the buildings life this produced a net present value (NPV) of over -20,000 Euro. Some of the upgrades had a larger impact for every Euro spent, and we did our best to prioritize them for the client. We concluded that PassivHaus is a great tool for energy efficiency but it is not always practical to upgrade a home all the way to the PassivHaus standard. It is only achievable within a reasonable budget when free solar energy from the sun can be used to reduce the heating load of the building.

I have attached a copy of our final report here. It contains more detailed information about the project and our upgrades.

Students and faculty involved in the Ireland Exchange

Receiving my certificate from Dan O'Sullivan of I.T. Carlow