We discussed that a well-sized Solar PV array may not be possible due to the installation of new Velux windows. However, I have based your system on a 4kWp array, which may be split over the South/North elevations of the roof. This proposal is indicative and would require further input from an installer to establish the possible array.

I have included Solar PV within 'Phase 1' as it could be cost-effective to install in-line solar panels during the repair and insulation works to the existing roof. If you choose to consider Solar PV at a later date, a subsequent cost for scaffolding will be required. In-line Solar Panels may be difficult to install following the installation of room-in-roof insulation; therefore, a mounted system would be the more appropriate choice if you wish to install PV at a later date.

If you choose to incorporate a new roof, Velux windows, Room-in-Roof insulation, and Solar PV, we would look to appoint a single contractor capable of carrying out all measures and repairs to ensure quality and continuity of work.

I've not included a battery in these phases because as discussed we will keep the potential outside locations for it free for an Air Source Heat Pump. There is always the possibility to add a battery later with more data about electricity generation and how well it matches to your demand profile, and after a heat pump is installed so we have certainty about a potential location.

Repairs to Roof, New Velux Windows and Upgrade Room-in-Roof Insulation

We discussed during our phone call the inclusion of roof repairs and the installation of three Velux windows within the first phase of your Retrofit Plan. These costs are estimated based on square meters and would require further input from contractors to provide accurate costs.

During our survey, it was noted that the stud walls in the roof room were insulated with 75mm mineral wool, which was in poor condition. The joists beneath the loft boards have 75-100mm of loose fill vermiculite/cellulose-type insulation, which could possibly contain amphibole asbestos. No insulation was observed on the rafters above the sloped ceiling.

As part of the roof repairs or replacement works, we recommend upgrading the insulation in the room-in-roof. This should be designed to encapsulate the entire roof space while maintaining ventilation. In our telephone conversation, we discussed that removing plasterboard and replacing it with insulated plasterboard may be too disruptive to consider. Therefore, we should explore options to insulate from above as part of the roofing works, creating a 'warm roof' system. Although this method can be more costly than insulating from the inside, it reduces disruption during the works. The process is as follows:

1. Roof trusses and purlins are exposed by removing tiles or slates, battens, and counter-battens.
2. A sloping base is constructed by affixing wooden panels or boards to these exposed elements.
3. A damp-proof membrane is securely attached to this newly formed base.
4. Next, insulation is applied, typically consisting of rigid panels such as extruded polystyrene, polyurethane, or wood fibers, ensuring enhanced thermal efficiency.
5. Finally, a fresh set of battens and counter-battens are installed onto a rainscreen membrane, providing a foundation for the reinstallation of tiles or slates.

If the option to insulate from the exterior is considered, then the existing vermiculite/cellulose-type insulation beneath the joists may not be disturbed. However, any materials suspected of containing asbestos should be tested by an appropriately qualified person, and appropriate removal techniques should be adopted if there is any doubt that the material may be disturbed.

Although our software does not predict significant annual savings or EPC improvement from this measure, fully insulating your roof space will improve the thermal comfort of your room-in-roof, with actual savings likely to be higher than predicted.

We recommend decentralised mechanical extract ventilation to ensure there is suitable ventilation in the kitchen and bathroom to prevent a build up of moisture. This means standalone extractor fans that can be toggled and/or humidity controlled.

Extraction ventilation over the cooking area should be planned into the kitchen design and the appropriate ducting installed. A cooker hood is recommended with an intermittent air extraction rate of 60l/s (or 213m3/h).

A continuous extractor fan with humidity sensor is appropriate to reduce risk of damp and mould in the bathroom.

An uninsulated suspended floor can result in up to 30% of the heat loss from a building – especially when the crawlspace is heavily ventilated as indicate by the air bricks in the walls outside. There are two main installation options:

1) to add insulation between the ground floor joists - either using rigid boards or a insulating wool (i.e. mineral wool). The floorboard may required to be lifted and furniture/floor removed to allow for the installation

2) a vapour-open spray foam insulation which can be completed without lifting the floorboards. This requires less disruption but will require a technical survey to check the humidty levels under the floor. The cost of any replacement flooring is not included in the pricing and should be taken into account when selecting the option to take forward.

There is a flat roof extension to the rear of the property where the kitchen is located and also an (assumed) uninsulated front elevation.

Insulating the roofs can significantly reduce heat loss - up to 20% of heat can be lost through the roof, so we are recommending flat roof insulation. Flat roofs have a longevity of approximately 15 years.

The insulation can be placed either above or below the roof. If the insulation is placed above the roof, the roof itself stays warm. For this reason, it is called ‘warm deck’ insulation. If the insulation is placed below the roof, the roof itself will be cold.

Warm deck insulation has advantages over cold deck insulation but is more expensive because of the significant cost of re-roofing. This method removes the possibility of condensation forming on the underside of the deck, eliminates damp and has the added advantage that it does not disrupt the living space within the dwelling. Unlike the cold roof method, the thickness of insulation you can install is not limited by the depth of the timber rafters/joists.

The cost included assumed "cold deck" insulation as the costs of re-roofing are not included. Ensuring this is sufficient ventilation to manage moisture in this space will be essential.

Currently the door from the kitchen to the garage is wooden with roughly 50% single glazed glass. This will mean there is significant heat loss going from the kitchen into the garage due to lack of insulation and lack of seal between the door and the frame.

Replacing the wooden back door with a insulated UPVC or composite door will significantly reduce heat loss and draughts in the kitchen space, due to improved thermal performance and increased air-tightness.

Air Source Heat Pumps, when installed correctly alongside the upgrade of existing pipework and radiators, can significantly reduce carbon emissions, as demonstrated by the Annual CO2 Savings. However, since electricity is currently more expensive than gas, the energy bill savings are typically lower than expected.

During our discussion, we briefly considered the installation of an Air Source Heat Pump but determined that addressing the roof and single glazing should take priority. In retrofit projects, a "Fabric First" approach is often encouraged, as the most cost-effective energy is the energy we don't consume. However, if you aim to significantly reduce your carbon emissions, it may be worth considering the early installation of an Air Source Heat Pump in your plan.

Please note that extensive upgrades to pipework and radiators are often necessary, including increasing the size of existing radiators, particularly in older properties. Contractors should conduct a Heat Pump assessment before submitting their proposal to determine the extent of the required works for heat pump installation. Grants are currently available for Air Source Heat Pumps in homes that have a valid Energy Performance Certificate (EPC) with no outstanding recommendations for loft or cavity wall insulation (source: link). The grant levels for heat pumps have been increased to £7,500, with funding confirmed until March 2028.

By establishing the presence of cavity walls and insulating them, as well as ensuring proper loft insulation, you can improve the energy efficiency of your home and increase your eligibility for a heat pump in the future. As mentioned earlier, an EPC will be required after the insulation works to demonstrate that the lofts and cavities (if applicable) have been properly insulated.

I note there are new tariffs available specifically for heat pumps that may enable you to make even further savings. These could be investigated in the design stage when choosing an installer and potentially a new energy supplier.