The house is a case study of a deep retrofit by Cambridge Retrofit Hub. It’s a work in progress with 25% of the work completed so far. We’re learning and trying to show how a deep retrofit can transform a house’s comfort and energy use.
We wanted to demonstrate how deep retrofit could be done in Cambridge as the Irish do (even without the Irish grants). We’re using the AECB Carbonlite Standard as an achievable but still challenging target for retrofit. This will transform the comfort of the home, in terms of freshness and air quality because of the MVHR, and reduce heating demand by a factor of 4.
We used a classic retrofit process:
(1) Pre-project evaluation and heat loss study.
(2) Whole-house plan to decide which improvements to make.
(3) Retrofit design to check the impact of different renovation measures and ensure compatibility with the AECB Carbonlite Standard.
(4) Retrofit works supervised by a Retrofit Coordinator to check the quality of works and confirm documentation by contractors is complete.
(5) Checks at the end of the project on: air tightness, comfort, energy use, energy generated and water use. We wanted to achieve an exemplar deep retrofit and full house renovation (including a new kitchen and bathrooms).
There were some minor internal wall changes but no extension or loft conversion. We wanted to demonstrate a professional and cost-controlled retrofit in a relatively common and simple building archetype i.e. a 3 bed semi-detached house.
The insulated concrete floor was fast to install (2 days prep, 1 day to pour) and made pegging out of the Underfloor Heating pipes very easy. The installer was Tom Mayhew from Easyscreed. The hemp insulation and airtight membrane were carried out by casual labour working with skilled trades (Cameron Ford). An EWI contractor has not been selected yet.
VENTILATION INSTALLER: Self installed
We’ve used a Zehnder unit in 2 other projects and it’s a reliable high-end product. The MVHR is installed but not yet commissioned (awaiting plastering and fitting of valves in rooms).
Windows with Deceuninck profiles not yet ordered, but used on previous projects; several fabricators used for pricing.
Performance of the solar arrays is estimated using the ‘EasyPV’ calculator. Similar sized systems on other properties have provided 81% of direct electricity (from solar PV and Battery).
Conga have started to install pipework but are awaiting other retrofit works before continuing. They are a good installer with massive demand for their products. We are hoping they find another installer contractor for Cambridge soon to meet the demand for installation and future maintenance and servicing.
Ground workers installed the outside tank, ducts and pipework; the controller and grey water plumbing was self installed (JG Speedfit).
BUILDER/CONTRACTOR: TBA
Retrofit is a complex process, especially when doing a full house refit at the same time.
OUR TOP TIPS
| Energy Consumption | Electricity (kWh) | Gas (kWh) | Wood (kWh) | Total (kWh) |
|---|---|---|---|---|
| Before | 1500 | 15000 | 0 | |
| After | 800 | 0 | 0 |
| Carbon Footprint | kgCO₂e/m² | kgCO₂e/person |
|---|---|---|
| Before | — | — |
| After | — | — |
* Wood logs estimated at 2,000 kWh/m³. Carbon factors are applied according to the project year. Where a project start or end date is not provided, 2026 is assumed.
