nZEB14 - school presentation
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View my nZEB School presentation from the DIT National Retrofit Conference 2014 held in Bolton Street on 6 June 2014. This is based on the result of work from our Postgraduate Diploma in Retrofit Technology, the semester 3 project in a nested 2.5year, part-time MSC in Retrofit Technologies. Students learned the PHPP energy metric and applied it tot he retrofit of a 1930s school building.
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nZEB14 - school presentation
- 3. 80 A2 90 National Schools and nZEB2:
- 5. Information
- 8. Daylight
- 9. Base Build to Enerphit 528 kWh/m2a 25 kWh/m2a
- 10. Base Build to Enerphit 528 kWh/m2a 25 kWh/m2a
- 11. Base Build to Enerphit 528 kWh/m2a 25 kWh/m2a
- 18. nZEB Six-pack 1. Geometry optimisation 2. Surface temperature 3. U-value calculation 4. Airtightness specification 5. Thermal bridging calculation 6. Hygrothermal modelling nZEB Six-pack Skills for the new digital construction
Editor's Notes
- 90% of Europe’s buildings retrofitted to a Building Energy Rating of A2 (45kWh/m2a). That’s the nearly Zero Energy Buildings challenge. Under the EPBD, nZEB applies to retrofit where 25% of floor area is refurbished. Or where 25% of the elevation is refurbished. It means that simply changing the windows will bring you over the threshold for nZEB.
- I would like to look at part of the skills set required and I invite all three professions currently designated as assigned certifiers in the Republic of Ireland by the Minister of the Environment under S.I 9 of 2014, to view the nZEB skill set DIT have identified as graduate attributes for our up-skilling off the building professions to meet the nZEB challenge. We have taken a school retrofit as a vehilce to imbed learning around the nZEB standard and used the Passive House refurbishment metric “Enerphit” to define the energy goal. All students achieved a space heat demand of 25kWh/m2a in their school retrofit study.
- Several passive house schools have been built in Ireland, here are some examples. This is the first time that the passive house standard has been applied to a school retrofit project in Ireland.
- DoES were very generous in providing very detailed construction information on the chosen school from their extensive database of blueprints.
- The building was modelled in BIM to ensure that a full understanding of the construction was developed in the minds of the students. It is impossible to model a building without understanding its construction, unlike 2D drawings where it is possible to draw unrealisable design details, or designs which defy the logic of a subsequent building process. Part of the skills-set is understanding the geometry of the physical building in detail. The target project is a simple 4-classroom school built in the 1930s and listed for demolition due to the cost of heating and its plan inflexibility.
- All except MVHR are required under Irish Building Regulations, Part L 2011 as they apply to residential development. MVHR is often required to achieve the final energy target for residential buildings, but imperative for a school building where ventilative heat losses are based on occupancy and each classroom has been designed to accommodate 25 people.
- Students were required to achieve the daylight factor of 4.25 stipulated in the DoES guidelines for school buildings. Achieving this target was only possible by an intervention into the form of the building to accommodate large areas of rooflighting. The metric influences the form (or “Form follows Function”).
- Insulation halves the space heat demand
- Airtightness haves it again. Airtightness is not mandatory in Ireland at present, but should be because of the energy savings it can achieve. It also protects the building fabric from deterioration as a result of interstitial condensation.
- MVHR more than halves the residual space heat demand again. Enerphit in 3 steps: insulation, airtightness and MVHR. Adding solar hot water (renewable solar energy) does not reduce space heat demand but reduces the primary energy requirement for the generation of hot water. Shading (required to control overheating) increases the primary energy use by requiring artificial lighting to be needed for slightly longer over the year to compensate for the impact of the solar shading, even with the use of additional rooflighting.
- I00 people get to spend 6 hours per day in 20degC, with 100% fresh air, good daylighting and no draughts or mould growth and, in the process, save 500 kWh/m2a. If this were regarded as an average school building, the energy savings every year from the refitting of the entire school building stock to Enerphit standard would amount to €86million. It would cost around €1/2million per school to refit to this standard, so 170 schools could be refitted every year from the energy savings potential, i.e. no capital cost. That would solve the economic problems of Ireland. It would also significantly reduce the penalties Ireland is planning to pay for its failure to meet its national CO2 emissions targets. The solutions employed by students are based only on certified construction products and technologies currently in existence, there is no speculative design allowed. Any one of them could be implemented in a pilot project tomorrow.
- A key element in proving the project was the ventilation solution, this was one of the more sucessful solutions, and the lowest cost ne proposed.
- MVHR units located at plan extremities where balanced exhaust and intake are guaranteed, plant noise is contained and access for maintenance is not disruptive.
- Supply duct is within the heated envelope ensuring minimal sizing as no insulation is required.
- Return air path is via the architecture, not the engineering. High level extract grille behind blackboard leads to low level air transfer grille in corridor wall, corridor becomes return air plenum and extract is via the washrooms on either end of the building. Layout worked out in detail in 3D so can be fabricated off-site and assembled on-site. Minimum disruption with maximum efficacy. The building now provides 100% fresh air 24/7. CO2 levels are optimal for all weather conditions and all user demands. Stable internal temperature of 20degC for all but 5% of the school year (hot days) when opening windows are required to supplement the mechanical ventilation rates.
- Very significant overheating is reported by the PHPP software when the daylight factor demanded by the Dept of Education and Science brief is achieved (orientation is SE). This is only controlled by fitting summer by-pass to the MVHR system and by adding significant shading to the main elevation. Note that the added shading increased the space heat demand slightly as a result of a reduction in spring and autumn mid-day solar gains.
- These are the essential skills set required to deliver nZEB in buildings, new or retrofit. We choose to teach students these based on a retrofit project because there are more compromises required, it takes more ingenuity and the risks are more difficult to balance. We say, if you can do retrofit, new-build is easy. It is unwise to certify compliance with Irish Building Regulations without a “six-pack” of skills such as this.