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Extended Georgian cottage

insulation, secondary glazing, solar panels, batteries, and an air source heat pump
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Overview

Age/Period: Georgian/Victorian
Type: 2-storey detached
Years in residence: 39
No. Bedrooms: 4
Wall type: Ashlar stone
Area: Widcombe
Status: Conservation area

Key Features

Double glazed windows and doors
Secondary glazing
Internal and cavity wall insulation
Passive solar gain
Loft Insulation
Draught Proofing
Air Source Heat Pump (ASHP)
EV charger
Energy efficient appliances and lighting
Ground mounted solar PV and batteries

Introduction

When Edward and Alex Nash bought Lime Grove Cottage in 1984 as a ‘project’, it was derelict and had been condemned. The cottage has a long history, originally being a mill for sharpening tools. When the Nash’s acquired the property it had been used as a market garden for flowers supplying the hotels of Bath, in the same family for 7 generations. It was in a poor state following it’s rushed repair after bomb damage during the last war. The original small 2 bed cottage had a mix of domestic and industrially purposed rooms.

It was a busy time for the Nash’s, with Edward setting up a new architectural practice, Nash Partnership in the face of a recession and with a young family to bring up.

The land was split into two with a new house being built at the end of the garden to help fund the purchase of the cottage. The family spent their first year of ownership in a caravan in the garden while making the cottage habitable.

Over the subsequent years Edward and Alex embarked on a programme of multiple extensions and improvements. Living there in the early years allowed them to understand the energy dynamics of the site and the opportunity for passive design, leading to large windows to south and west, and how the location of the site offers shelter to winds from north and east. The cottage is an interesting case study in how the ideas and techniques around sustainable construction have evolved over the last 40 years.

More recently the Nash’s have seen their Zero Carbon journey as an obligation, needing serious attention, a commitment of time, part of their retirement planning, to be completed in stages.

Features

Given the multiple evolutions and extensions to the property, it’s probably easiest to describe its current evolution!

Insulation

The best practice techniques and materials of the time have been used at every opportunity to insulate the property.

A variety of insulation has been used:

  • 50mm polystyrene partial fill cavity linings
  • 50mm underfloor polystyrene insulation
  • Mineral wool loft insulation
  • Mineral timber insulated frame walls
  • Multifoil room in roof insulation
  • Celcon aerated insulated masonry blocks
  • Thermal wall boards
  • Insulated solid door panels

As an architect Edward is now more focussed on using breathable natural insulation in historic buildings and would be happy to talk about best practice being applied to Nash Partnership’s offices and a number of historic buildings they are working on in central Bath.

Draughtproofing

Edward and Alex have draughtproofed the property themselves, including windows and doors. They have also recently had brush strips fitted to the sash windows, and Mitchell and Dickinson Plexiglass magnetic secondary glazing.

Windows

The orientation of the windows in the extensions have been carefully thought out to maximise solar gain to reduce heating demand while avoiding overheating. The
house has a mix of single and double glazing. Edward particularly wanted to retain the aesthetics of traditional sash windows and have used secondary glazing where
appropriate.

Solar PV, batteries, and EV charging

In wanting to minimise their electricity consumption, and help charge their EV, the Nash’s wanted to maximise the onsite production of electricity. This was a challenge as individual roofs were too small, so they innovated and installed 9 solar PV panels (3.8 kWp) in April 2022 along the wall of their drive. Unable to find a proprietary
support structure for the PV they fabricated a bespoke one out of alloy tubing. They have also installed a large 10 kWh SolarEdge home battery which is charged from the solar PV and used later in the day when the sun goes down to save consuming electricity from the mains.

In it’s first year the solar PV yielded 37% of energy consumed by the house and for charging their EV.

Wood burners

The house has 2 wood burners. The burner in the lounge is notable because it more efficiently sources its air from outside the house via the cavity wall.

Air Source Heat Pump

In August 2023 an air source heat pump was installed with the help of a government £5K grant, replacing a gas boiler. The heat pump should reduce CO2 emissions by 90% and work well with the solar PV and battery.

To make the heat pump more efficient some of the radiators have been increased in size but the system continues to make use of the existing under-floor heating. The hot water cylinder has been installed outside the main house in a workroom to free up the space previously taken by 2 hot water cylinders in the main house.

Recycling of materials

Where possible building materials have been sourced onsite, so many of the walls use recycled bath rubblestone reducing the need and expense of sourcing from the rest of Bath.

Vegetable garden

They have an extensive vegetable garden at the back of the property watered by a well in the garden with an immersion pump. Part of their environmental philosophy is to minimise food miles and grow as much food onsite as possible.

Alex who was originally a teacher, retrained as a garden designer and horticulturist, and has created a lovely flower garden at the front of the property.

Remaining work

Now that Edward has recently retired there are a few items of outstanding work:

  • replace the home’s remaining halogen bulbs with LEDs
  • install a more intelligent control system to coordinate the solar PV, charging the car batteries, the home batteries and running the heat pump, all as efficiently as possible
  • insulate a few remaining ‘cold thermal bridges’
  • replace 40-year-old double glazing with new vacuum glazing which outperforms triple glazing
Contacts

ASHP: Sustain Heating
Solar: Eco-assist
Secondary glazing: Mitchell & Dickinson
General Advice & Planning: Nash Partnership