St Nicks

Centre for nature and green living

Victorian energy efficient retrofit

George Robinson

[You can watch George talk about his home project in this video and/or read the description below. Feel free to get in touch with York Open Eco Homes organiser Ivana ( who can relay questions to George if unable to answer directly. Please note that including links to companies on this page does not constitute their endorsement by St Nicks.]

George Robinson’s aim was to undertake a home upgrade (retrofit) that would have minimal visual impact on the house while achieving substantial improvements in comfort and energy savings. Partly thanks to local contractors and partly George himself, this standard Victorian terraced house is transforming into a modern, comfortable home that doesn’t cost the Earth to run.

By modelling the house in PassivHaus software, local architect Phil Bixby helped evaluate the relative impacts that different fabric adjustments were estimated to have and George’s work was then focused on four key areas:

George's insulation works YOEH2021

Internal wall insulation process

1. Insulation
We used a combination of woodfibre insulation (100mm on the walls and between floor joists), 100mm cork (for the kitchen where there was a greater risk of moisture) and upcycled 100mm plastic insulation in some places such as the pre-existing dormer bedroom. All floor insulation was done DIY while all internal wall insulation was done by a great local plasterer / insulator Craig Young.

George Robinson YOEH2021 fireplace removal

Fireplace and chimney removal

An important decision was whether the original chimney stacks should or should not be removed. In the end we decided, aided by the PassivHaus calculations, that removing them internally (but retaining the external stacks at the top of the house so as not to change the external look of the property) was the way to go. This allowed for larger areas of insulation to be installed more quickly, removed one of the key areas for heat loss (air up the chimney!) and meant overall we actually gained internal space despite having installed 100mm of insulation on all internal walls that were in direct contact with the outside.

To reduce waste, the original fireplace was reclaimed by a local fireplace restorer and all waste timber was taken by Leeds Wood Recycling.


George Robinson YOEH2021 airtightness measures

Foil backed tape and air membranes were key for air tightness in areas that would be decorated. Mastic (i.e. flexible sealant)
was used in more visible places.

2. Air tightness
Reducing heat loss of a home requires high levels of air tightness as well as insulation, which basically means making sure that heat doesn’t leak through draughts and faults in fabric. George had a test done by Northern Air Tightness Testing Services before the start of any works, which showed a rather leaky 12 air changes per hour. The higher the rate, the more energy is required to keep a house heated so George’s aim is 3-5 air changes – he’s already succeeded in halving the rate to 6. (For reference, the super efficient Passivhaus standard is up to 0.6, for which active ventilation is essential.)

A lot of attention was paid to improving air tightness throughout the house with DIY measures. All ground floor floors were membraned,  foil taping was used behind all skirting boards and around all points of exit from the property that could be boxed out (e.g. foul pipes). Mastic sealant was used for more visible areas such as electricity mains supply from the street to the fuse box.

George Robinson YOEH2021 bifold kitchen door

Bifold kitchen door

The test also revealed kitchen bifold doors and dormer room windows had poor air tightness despite being double glazed. These were replaced with FSC certified timber framed windows and bifold.


George Robinson YOEH2021 bathroom vent

Air vent and yet to be concealed ducting in the bathroom

3. Ventilation
Once we got rid of uncontrolled ventilation which leaks heat 24/7, we needed to ensure good fresh air supply. As part of the work we had radial ducting taken to every single room in the house with all air supply ducts insulated, allowing for more efficient central cooling should that be needed on in the future (let’s hope not!). These have been hooked up to a mechanical ventilation unit with heat recovery (MVHR). It’s a pretty amazing piece of kit that uses about the same electricity as a fridge (30W) but on winter days saves the property having to expend approximately 600W of heating cold air which otherwise would have come in if we had not undertaken the air tightness measures. It also manages air moisture as well as filters our air. The system, ducting runs and installation was undertaken by ADM Systems.


George's solar panels - thermal and PV

Solar panels – thermal on the left and PV on the right

4. Heating system and wider energy

We have had an 8kW air source heat pump installed to supply space heating needs and domestic hot water for the winter and shoulder months. During the summer our hot water is primarily met through solar heating (Navitron evacuated tubes). Additionally we installed PV panels and a Tesla battery – on sunny days we are totally off grid with some left over for the next day! The energy equipment and system was installed by T4 Sustainability with general plumbing carried out by Andy Fisher.

George's monitoring software

George’s monitoring software showing how the solar thermal system is doing

We have installed a home designed and built energy monitoring system (using a Raspberry Pi) that uses inexpensive sensors and pulse meters to monitor overall system performance across the heat pump, solar thermal, PV and battery. The aim is to show the extent to which we can demonstrate both the impact of the fabric adjustments on overall heating requirements but also the relative efficiency of this more modern equipment.

There is still lots to do but George estimates that heating demand will be 1/3 of what it previously was, and the heating system is free in the summer and hopefully 250% efficient in winter.

It already is a much more thermally comfortable home and a great local showcase of eco retrofitting. It will be fascinating to see what George’s achieved by York Open Eco Homes 2022!

This page was last updated 6 Dec 2021