Repairs to Roof, New Velux Windows, and Room-in-Roof Insulation Upgrade During our phone call, we discussed including roof repairs and the installation of three Velux windows in the first phase of your Retrofit Plan. The estimated costs are based on square meters, but further input from contractors will be needed for accurate pricing. Our survey found that the stud walls in the roof room are insulated with 75mm mineral wool, which is in poor condition. The joists beneath the loft boards contain 75-100mm of loose-fill vermiculite or cellulose-type insulation, which may contain amphibole asbestos. No insulation was observed on the rafters above the sloped ceiling. As part of the roof repairs or replacement, we recommend upgrading the insulation in the room-in-roof. This should fully encapsulate the roof space while maintaining ventilation. In our conversation, we noted that removing and replacing plasterboard with insulated plasterboard may be too disruptive. Instead, we should explore insulating from above as part of the roofing works, creating a ‘warm roof’ system. While this approach is more costly than internal insulation, it minimizes disruption. The process includes: Removing tiles or slates, battens, and counter-battens to expose roof trusses and purlins. Constructing a sloping base using wooden panels or boards. Attaching a damp-proof membrane to the new base. Installing rigid insulation panels, such as extruded polystyrene, polyurethane, or wood fibers, to enhance thermal efficiency. Installing a new set of battens and counter-battens on a rainscreen membrane, creating a foundation for the reinstallation of tiles or slates. If external insulation is chosen, the existing vermiculite or cellulose insulation beneath the joists may remain undisturbed. However, any materials suspected of containing asbestos should be tested by a qualified professional, and appropriate removal techniques should be used if necessary. Although our software does not predict significant annual savings or EPC improvement from this measure, fully insulating the roof space will enhance thermal comfort in the room-in-roof, with real savings likely exceeding predictions.

We discussed that installing a well-sized Solar PV array may not be possible due to the new Velux windows. However, I have based your system on a 4kWp array, which could be split between the south and north elevations of the roof. This proposal is indicative and would require further input from an installer to determine feasibility. I have included Solar PV in 'Phase 1' as it may be cost-effective to install in-line solar panels during the roof repair and insulation works. If you choose to install Solar PV at a later date, additional scaffolding costs will be required. In-line solar panels may also be difficult to install after room-in-roof insulation is in place, so a mounted system would be the more practical option for a later installation. If you decide to proceed with a new roof, Velux windows, room-in-roof insulation, and Solar PV, we would aim to appoint a single contractor to carry out all measures and repairs to ensure quality and continuity of work. I have not included a battery in these phases, as we agreed to keep potential outdoor locations available for an Air Source Heat Pump. A battery can always be added later, once we have more data on electricity generation and how well it aligns with your energy needs. This decision can also be made after installing a heat pump, ensuring we have a confirmed location for it.

We recommend decentralized mechanical extract ventilation to ensure adequate ventilation in the kitchen and bathroom, preventing moisture buildup. This involves standalone extractor fans that can be manually toggled or humidity-controlled. In the kitchen, extraction ventilation should be incorporated into the design, with appropriate ducting installed. A cooker hood is recommended with an intermittent air extraction rate of 60 l/s (213 m³/h). For the bathroom, a continuous extractor fan with a humidity sensor is recommended to reduce the risk of damp and mould.

The current door from the kitchen to the garage is wooden, with approximately 50% single-glazed glass. This results in significant heat loss due to poor insulation and a lack of sealing between the door and the frame. Replacing the wooden door with an insulated UPVC or composite door will significantly reduce heat loss and draughts in the kitchen, improving thermal performance and air-tightness.

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: 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 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.

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.