By Jonathan Kearns, Deborah A. Byrne and Charlotte J. Leck
The increasing emphasis on carbon reduction in buildings has created a new imperative for the adoption of the ultra low energy Passive House standard. With all new government and publicly-funded projects required to meet Zero Carbon Targets by 2030 and all existing buildings by 2050, High Performance (HP) buildings generally, and Passive House (PH) buildings in particular have a vital role to play.
These publicly-funded projects are often procured through traditionally formulated processes, that are not always well-suited for PH projects. Rather, a successful project begins with a complementary procurement process, as the high-level performance targets of PH buildings need rigour in design and construction. Therefore, they require the ideal team and a specific process for implementation.
Passive House uses building science and biophysics to assess what the building envelope must provide to achieve high levels of occupant comfort and energy efficiency. There are seven main performance requirements to successfully meet the Passive House standard and these are modelled using the Passive House Planning Package (PHPP). The PHPP assesses the overall building performance for heating, cooling and total energy demand. For over 25 years, monitoring of buildings designed to the PH standard in Europe has consistently shown that this performance standard has been maintained over time.
With these high-performance targets, there is a requirement for an integrated approach to design, in which the general contractor or construction manager is involved from the outset.
The Ideal Team
Under ideal circumstances, all those involved in a PH project would be experts, each with vast experience in PH and an understanding of their role within the team. These would include:
1. A PH specialist architect-led design team.
2. Expert trades directed under a PH-expert construction manager.
3. A client who understands the standard and the rigour and commits to the design process (front end engineering design – FEED) and construction methodology.
4. Multiple suppliers that can offer materials and equipment that are Passive House compliant.
Unfortunately, the industry does not yet have the capacity to match this ideal, but those with the requisite experience can provide guidance for those not yet engaged in this market. The long-term success of a Passive House project does not rest solely on the performance of the building after substantial completion, but also includes the effective implementation of all stages of the design and construction. Integrated design leads to fewer “unknowns” during construction, supports the rigour required on site, and reduces the risk of cost overruns.
Shortcomings of Traditional Procurement Methods
Traditional procurement methods give the highest weighting to the architect/prime consultant with the most experience of the building type under consideration, together with the lowest price. Similarly, the industry prefers to hire the general contractor using CCDC 2 Stipulated Sum 2008. Reference: http://www.ccdc.org/document/ccdc2/.
The problems with this approach are:
1. Experience: The ability of the Prime Consultant is scored only on experience related to building type and not on professionalism or years of expertise. “Relevant experience” typically means a building of a similar type and scope built within the last 5 years, ignoring the fact that buildings performing to this level don’t currently exist. This means the architect with the most valuable HP building expertise will not get the appropriate credit.
2. Consultant Fees: Passive House Projects are currently more expensive, running at a premium of 5-10%. The experienced PH architect will price accordingly, quoting a higher fee than the architect who doesn’t fully understand the scope of PH. Again, the architect with the most relevant experience will score low.
3. Sustainability: The Scoring Matrix ignores the fact that the HP building scope, whether it be PH or another building standard, is a fundamental basis of design. It drives the engineering, which informs the architecture and should be scored as such. PH or HP should always be a core component of the scope, never a “nice to have” add-on – this simply won’t work.
4. Experience with the Team: The prime consultant for an HPB/PH will want to hire the engineering team that understands the intricacies of this type of project. Again, scoring focuses on typology and the relationships with the prime. For PH projects, the prime consultant must be allowed to hire the best team for the project, which may not be the team that they have worked with many times before.
5. Budget: High Performance buildings are exactly that, performing much better than those simply built to code. Therefore, the types of materials and construction methods used must be among the best available in the market. This will ensure the building is durable and resilient with an extended life cycle. A knowledgeable prime consultant, concerned the budget is too low, may withdraw from the procurement process, rather than take on an underfunded project.
6. Schedule: The schedule also needs to reflect the PH scope. The design schedule is extended to reduce the number of on-site changes and the construction schedule will increase to accommodate additional quality assurance and quality control protocols.