Plans showing proposed building in Chester

EnerPHit Retrofit 6: planning the schedule of works

Posted on 14/12/22

The sequencing of the works for Matt’s Passivhaus EnerPHIT project has been determined by a number of factors. In his sixth blog about his retrofit at his family home, he explains how important the scheduling of the works is for maximum efficiency.

Starting from the bottom….and the top 

When we purchased the bungalow, we knew full well that all the ground floor slabs had settled. In most cases, this settlement had caused the Damp Proof Membrane below the floors and the Damp Proof Course within the walls to separate. This had allowed moisture a route to track into the property, which had caused issues with the plasterwork and needed rectifying before we could make a start on redecorating rooms and fitting a new kitchen and bathroom.

The loft was another area of particular concern. Currently, it still contains quite a lot of redundant wiring and the remains of an old central heating system, and it also houses two tanks from the current hot water system. We will be removing all of these to make way for a new heating and hot water system. It makes sense to do this before we upgrade the loft insulation. Added to that, the house currently has no mechanical extraction and so is particularly prone to condensation/high humidity levels. This means we will be adding the Mechanical Ventilation with Heat Recovery (MVHR) system early in the scheme of works. Once these elements and a slight amendment to the existing wiring has been completed, I can remove all the degraded insulation from the loft and lay new insulation neatly and completely to ensure it works effectively.

The house is currently heated by electric panel heaters that are extremely expensive to run. When we moved in during March this year, we were using up to 40kW per day to heat the house; and that was to keep the house “not cold” rather than comfortably warm. The hot water system is also rather ancient and relies solely on an immersion heater, while the showers are electric.

Air source heat pump installation 

Installing a new air source heat pump (ASHP), heating a 250l cylinder, will allow us to heat the house via wet radiators and underfloor heating (UFH) more efficiently (ASHP’s have an output of about 3kW for every kilowatt you input) as well as switch away from the electric showers. The system will be supported by solar thermal (water) panels in the summer months and a diverter system to send any spare electricity generated by the PV panels to an immersion heater. Both of these will significantly reduce the electricity demand, which should already be substantially lowered by the increased thermal performance and utilisation of an ASHP and the improved insulation.

Scheduling so some tasks overlap 

All of the above will form the first tranche of works, or, as defined in the variants (upgrades) page of the PHPP project file, “Variant 1”.

Variant 2 will involve the replacement of some of the windows, including the remaining single glazed timber windows and door. I am also going to externally insulate the gable wall within the garage – this does not need planning permission, unlike the remainder of the external insulation. This will make a big difference to two of the bedrooms so is a worthwhile addition as we approach winter.

Time wise, some of the above tasks will overlap with one another but, as I am doing the majority of the work myself, planning the windows as part of Variant 2 will allow me to get the majority of Variant 1 completed while I wait the ten weeks or so for the windows to be manufactured.

Looking ahead to spring and fitting solar thermal panels 

Next year, we can make a start on Variant 3. This will comprise fitting the solar thermal panels and additional PV array. As this is likely to be during next spring/summer it will spread the costs a bit and buys me time to get the first two variants completed and have a bit of a rest too if I’m lucky! In reality, we won’t noticeably benefit from the solar thermal and PV panels until the middle of March.

Planning application for external insulation 

I am currently planning Variant 4 to be the external insulation, which is subject to a planning application and approval. I’ll also need planning permission to replace the better performing remaining, double glazed units as I want to slightly change their size and appearance.

There is clearly a lot of work to be done. Fortunately, the way the PHPP variants system is set up makes it very easy to plan it in a way that makes sense on the ground and that can be checked to ensure that any alterations do not impact on the fabric of the build until the works have been completed. It feels good to know that by the time this winter really kicks in, our heating load will be reduced to about 35% of what it has been previously.

If you are interested in finding out more about Passivhaus, which can be applied to applied across all construction sectors, from commercial and industrial, to medical and educational, please get in touch with us.

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