Passive House Retrofit – Retrofitting to the EnerPHit standard

Existing building stock can be upgraded to achieve a standard close to the Passive House standard. EnerPHit is not as demanding as the new build standard but can present its own challenges in implementation.

Why refurbish?

Retrofitting an existing building with Passive House components and utilising Passive House principles brings almost all the benefits of building a new Passive House. Many people opt to refurbish existing buildings rather than a new build and these buildings will have continued use for decades to come. However, these existing buildings use even more energy than conventional new builds and so offer an opportunity to deliver even greater energy savings.

Retrofitting with EnerPHit

The EnerPHit standard was developed in 2010 specifically for retrofits. The standard is not as demanding as the new build Passive House standard. For example, the limit for heating demand is 25kWh/a per square metre of living area in the EnerPHit standard, compared to 15kWh/a per square metre of living space in the Passive House standard. Existing buildings present challenges that cannot be feasibly adapted (e.g. built-in thermal bridges, poor orientation) so allowances are made for this. However, the EnerPHit standard will ensure that comfort levels, structural longevity and energy efficiency are all vastly improved.

Saving Energy = Saving Money

Retrofitting to EnerPHit will incur additional costs to a project so it is crucial to optimise the renovation measures that would have been necessary anyway. For example, the energy efficiency provided by additional insulation and Passive House windows can lead to significant savings being made on a conventional heating system (if one is still required at all). Additional costs can be compared to the annual energy saving benefit, even down to a component by component basis.

Is refurbishing worth it?

An EnerPHit refurbished building lessens both the financial burden of the occupant and the environmental impact of the building. Combined with the improved comfort of such buildings and the reduced risk of structural damage, this ensures that retrofitting to the EnerPHit standard is worthwhile.

Additionally the value of the property for both sale and rent increase significantly with the low energy requirements of such buildings being particularly attractive.

Retrofitting to the highest standard

Energy efficient measures for any one part of a building are at their most affordable when that part already needs renovations. For example, you will already be paying labour costs and likely incurring additional costs such as scaffolding. As such, any renovation that is worth doing is worth doing well. If an all in one Passive House retrofit is not possible, then a step by step approach can be a way forward.

How much insulation?

High insulation levels should be seen as an affordable insurance policy against energy prices hikes. If you don’t require as much energy for heating, you will be far more resilient to rising costs. Insulation can be applied either inside or outside the building, with both presenting their own benefits in a retrofit. Depending on the choice of insulation, 24-32cm thickness would usually be optimal.

Achieving airtightness in retrofits

There are many options for airtightness in a retrofit, though these will mostly depend on the project. For example, the plaster coat could act as the airtight layer in a building with concrete ceilings, but is less likely to be effective with timber beam ceilings due to the repeated joist connections.

Reducing demand

A comprehensive building fabric, heat recovery ventilation system and an airtight building envelope will all reduce heating demand in a building. As such, other sources of energy use account for a far higher percentage of the total energy requirement for the building in an EnerPHit standard retrofit.

For example, domestic hot water and lighting should both be addressed in a retrofit. Pipe insulation, low energy light bulbs and efficient white goods are all good choices in maintaining a low energy demand for the building.

Efficiency first

With Passive House, we think of fabric first. Or in other words, make the building as efficient as possible rather than looking to generate additional energy to cover your needs. Reducing consumption is an affordable, sustainable way to live with the added benefit of strong resiliency against energy price hikes.