{"id":326902,"date":"2025-05-22T10:00:09","date_gmt":"2025-05-22T09:00:09","guid":{"rendered":"https:\/\/detail-library.co.uk\/?p=326902"},"modified":"2025-05-19T18:02:49","modified_gmt":"2025-05-19T17:02:49","slug":"fabric-upgrades-and-heat-pumps-finding-the-sweet-spot","status":"publish","type":"post","link":"https:\/\/detail-library.co.uk\/fabric-upgrades-and-heat-pumps-finding-the-sweet-spot\/","title":{"rendered":"Fabric Upgrades and Heat Pumps \u2013 Finding the Sweet Spot"},"content":{"rendered":"

[et_pb_section fb_built=”1″ specialty=”on” padding_top_1=”80px” padding_top_bottom_link_1=”false” padding_left_right_link_1=”false” admin_label=”Intro” _builder_version=”4.22.2″ custom_padding=”3px|||||” global_colors_info=”{}”][et_pb_column type=”2_3″ specialty_columns=”2″ _builder_version=”4.16″ custom_padding=”|||” global_colors_info=”{}” custom_padding__hover=”|||”][et_pb_row_inner _builder_version=”4.16″ global_colors_info=”{}”][et_pb_column_inner saved_specialty_column_type=”2_3″ _builder_version=”4.16″ global_colors_info=”{}”][et_pb_post_title meta=”off” featured_image=”off” _builder_version=”4.16″ title_font=”Montserrat|600|||||||” title_text_color=”#000000″ title_font_size=”64px” title_line_height=”1.2em” title_font_size_tablet=”50px” title_font_size_phone=”24px” title_font_size_last_edited=”on|desktop” locked=”off” global_colors_info=”{}”][\/et_pb_post_title][\/et_pb_column_inner][\/et_pb_row_inner][et_pb_row_inner _builder_version=”4.16″ global_colors_info=”{}”][et_pb_column_inner saved_specialty_column_type=”2_3″ _builder_version=”4.16″ global_colors_info=”{}”][et_pb_text admin_label=”Intro Text” _builder_version=”4.27.4″ text_line_height=”1.8em” max_width=”600px” module_alignment=”center” locked=”off” global_colors_info=”{}”]<\/p>\n

In March 2024, the National Audit Office (NAO) reported that heat pump uptake was slower than expected, despite the Boiler Upgrade Scheme (BUS) offering a \u00a37,500 grant to replace an existing heating system with a new heat pump.<\/span><\/p>\n

The target is 600,000 installs per year by 2028, which at the current pace is highly optimistic. One of the main blockers has been the cost to run a heat pump, not helped by a sceptical media that loves to promote the heat pump failures rather than celebrate the success stories.<\/span><\/p>\n

[\/et_pb_text][\/et_pb_column_inner][\/et_pb_row_inner][\/et_pb_column][et_pb_column type=”1_3″ _builder_version=”4.16″ custom_padding=”|||” global_colors_info=”{}” custom_padding__hover=”|||”][et_pb_image src=”https:\/\/detail-library.co.uk\/wp-content\/uploads\/2025\/05\/FI-Heat-Pump.png” alt=”_FI Heat Pump” title_text=”_FI Heat Pump” admin_label=”Image 00″ _builder_version=”4.27.4″ custom_margin=”|-9vw|||false|false” global_colors_info=”{}”][\/et_pb_image][\/et_pb_column][\/et_pb_section][et_pb_section fb_built=”1″ admin_label=”Quote Section” _builder_version=”4.21.0″ use_background_color_gradient=”on” background_color_gradient_direction=”90deg” background_color_gradient_stops=”#ffffff 70%|#00c4cc 70%” background_color_gradient_start=”#ffffff” background_color_gradient_start_position=”70%” background_color_gradient_end=”#00c4cc” background_color_gradient_end_position=”0%” custom_padding=”50px||3px||false|false” background_last_edited=”on|phone” background_color_gradient_stops_phone=”#ffffff 95%|#00c4cc 95%” background_color_gradient_start_position_phone=”95%” locked=”off” global_colors_info=”{}”][et_pb_row _builder_version=”4.16″ max_width=”900px” global_colors_info=”{}”][et_pb_column type=”4_4″ _builder_version=”4.16″ global_colors_info=”{}”][et_pb_image src=”https:\/\/detail-library.co.uk\/wp-content\/uploads\/2021\/03\/magazine-18.png” _builder_version=”4.16″ custom_margin=”||50px||false|false” global_colors_info=”{}”][\/et_pb_image][et_pb_text _builder_version=”4.27.4″ text_font=”Cardo||||||||” text_text_color=”#2a2a2a” text_font_size=”42px” text_line_height=”1.4em” text_orientation=”right” text_font_size_tablet=”36px” text_font_size_phone=”24px” text_font_size_last_edited=”on|desktop” global_colors_info=”{}”]<\/p>\n

This is not another article asking \u201c<\/span>are heat pumps good or bad<\/span><\/i>?<\/em>\u201d They are good.\u00a0<\/span>Next question.<\/span><\/p>\n

[\/et_pb_text][et_pb_divider divider_weight=”6px” _builder_version=”4.16″ _module_preset=”default” global_colors_info=”{}”][\/et_pb_divider][\/et_pb_column][\/et_pb_row][\/et_pb_section][et_pb_section fb_built=”1″ admin_label=”Blog Post Body” _builder_version=”4.22.2″ collapsed=”off” global_colors_info=”{}”][et_pb_row _builder_version=”4.22.2″ _module_preset=”default” custom_padding=”100px||||false|false” global_colors_info=”{}”][et_pb_column type=”4_4″ _builder_version=”4.19.5″ _module_preset=”default” global_colors_info=”{}”][et_pb_text admin_label=”Intro Continued” _builder_version=”4.27.4″ _module_preset=”default” custom_padding=”20px||||false|false” global_colors_info=”{}”]<\/p>\n

Nesta\u2019s heat pump survey from May 2023 reported high levels of satisfaction overall from heat pump users across building types of all ages. Over 70% of respondents were either \u2018very satisfied\u2019 or \u2018fairly satisfied\u2019 with 8 of the 10 survey attributes (which covered things like running cost, noise, safety, ease of use etc.). Nearly three-quarters (73%) of heat pump users had the same or higher levels of satisfaction with their heat pump compared to their previous heating system.<\/span><\/p>\n

So, this is not another article asking <\/span>are heat pumps good or bad<\/span><\/i>? They are good.\u00a0<\/span><\/p>\n

Next question.<\/span><\/p>\n

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(Source: Nesta Heat Pumps: A User Survey May 2023)<\/span><\/em><\/p>\n

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Is a Heat Pump Right for My Home?<\/h2>\n

[\/et_pb_text][et_pb_text admin_label=”Is a Heat Pump Right for My Home?” _builder_version=”4.27.4″ _module_preset=”default” custom_padding=”20px||||false|false” global_colors_info=”{}”]<\/p>\n

That is a better question, and the one that the retrofit industry is attempting to answer for curious homeowners across the UK. Many factors affect the successful switch to a heat pump including the existing pipework, radiator sizes, the hot water tank, external placement and noise. This article will look at the role fabric plays in the suitability of a heat pump including the current industry debates around <\/span>Fabric First<\/i><\/b> and <\/span>Fabric Fifth<\/i><\/b>.\u00a0<\/span><\/p>\n

In order to isolate the impact of the fabric, for this article we\u2019ll assume in all scenarios that the heat pump is an air-to-water \u2018air source\u2019 and is well designed, installed and commissioned.\u00a0<\/span><\/i><\/p>\n

We have the coldest and leakiest homes in Europe and big problems with users experiencing discomfort. Many potential heat pump customers regretfully cite this as a reason they feel their home is not appropriate for a heat pump, as it is too cold and leaky. Poor fabric is not a technical barrier to installing a heat pump but will be a cause of poor performance. For most homes, some fabric upgrades are encouraged alongside a heat pump, but how much is enough? Where is the sweet spot?<\/span><\/p>\n

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Bespoke Solutions<\/h2>\n

[\/et_pb_text][et_pb_text admin_label=”Bespoke Solutions” _builder_version=”4.27.4″ _module_preset=”default” custom_padding=”20px||||false|false” global_colors_info=”{}”]<\/p>\n

Many retrofit professionals who support heat pump uptake prefer a tone that is positive but realistic. It is rarely straightforward, but in simple terms, a home running a boiler, hot water tank and wet radiator system can use a heat pump to do the same job. The answer is normally <\/span>\u2018yes, but\u2026\u2019<\/span><\/i>\u00a0<\/span><\/p>\n

The architect\/designer\u2019s role will be to identify the fabric upgrades that will maximise the effectiveness of the switch, using insulation and airtightness measures to support the retention of heat and raise comfort levels. This comes down to good understanding of the home\u2019s current performance, high-quality detailing and specification (using a Whole House Approach), focusing on the interactions as the main points of weakness. The growing collection of retrofit details in the Detail Library makes this job far easier.<\/span><\/p>\n

[\/et_pb_text][\/et_pb_column][\/et_pb_row][et_pb_row _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}”][et_pb_column type=”4_4″ _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}”][et_pb_divider divider_weight=”6px” _builder_version=”4.27.4″ _module_preset=”default” max_width=”70%” module_alignment=”right” custom_padding=”10px||||false|false” global_colors_info=”{}”][\/et_pb_divider][et_pb_text admin_label=”Typical Energy Usage (H2)” _builder_version=”4.27.4″ _module_preset=”default” custom_padding=”80px||||false|false” global_colors_info=”{}”]<\/p>\n

Typical Energy Usage<\/h2>\n

[\/et_pb_text][et_pb_text admin_label=”Typical Energy Usage” _builder_version=”4.27.4″ _module_preset=”default” custom_padding=”20px||||false|false” global_colors_info=”{}”]<\/p>\n

For those motivated by carbon reductions, removing fossil fuels is the single most effective action you can take. The affordability of heat pumps in the UK is linked to the pricing of grid energy. Currently, one unit of gas is 4x cheaper than one unit of electricity. The government has committed to rebalancing this \u2018spark gap\u2019 which is seen as hampering moves to all-electric heating. There are wider issues around grid capacity too, but compared to mainland Europe, our electricity is disproportionately expensive and makes electric heating unattractive.<\/span><\/p>\n

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Nesta study motivations for installing a heat pump.<\/span><\/i><\/p>\n

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The way energy is explained to consumers is also mystifying, so it does not help them compare apples with apples when considering a shift in the way they manage their home\u2019s energy.\u00a0<\/span><\/p>\n

Anyone who has bought or sold a house is familiar with an EPC certificate, giving the home an energy rating, like you find on whitegoods. EPCs currently still favour gas usage as the underlying calculation engine was designed to explain <\/span>energy costs<\/span><\/i>, particularly Primary Energy, which is fundamentally not the same energy metric that consumers see on their energy bills, which is delivered energy or \u2018in-use\u2019 energy.\u00a0 Currently, a move to heat pump may reduce your EPC score unless you do lots of fabric upgrades alongside it. Until the new calculation method arrives, this distorts the positive effects heat pumps make to home energy use. <\/span><\/p>\n

[\/et_pb_text][\/et_pb_column][\/et_pb_row][et_pb_row _builder_version=”4.24.2″ _module_preset=”default” global_colors_info=”{}”][et_pb_column type=”4_4″ _builder_version=”4.24.2″ _module_preset=”default” global_colors_info=”{}”][et_pb_divider divider_weight=”6px” _builder_version=”4.27.4″ _module_preset=”default” max_width=”70%” module_alignment=”left” custom_padding=”10px||||false|false” global_colors_info=”{}”][\/et_pb_divider][et_pb_text admin_label=”Heat Demand (H2)” _builder_version=”4.27.4″ _module_preset=”default” custom_padding=”80px||||false|false” global_colors_info=”{}”]<\/p>\n

Heat Demand<\/h2>\n

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Note how the Losses and Gains are equalised by the large red block representing the heating demand supplied by the heating system
(Source: extract from a PHPP model)<\/span><\/i><\/p>\n

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We currently use our boilers to make up the deficit of heat in our homes. Imagine a big pair of scales, with gains and losses on either side. The heat gains include solar radiation through windows and heat generated by people, pets and appliances.<\/span><\/p>\n

On the other side, the losses include heat escaping through the fabric, via ventilation and air leakage. For most UK homes of average thermal & airtight performance, the losses far outweigh the gains, so a high heating demand is needed to balance the scales. <\/span><\/p>\n

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For a typical home running a gas boiler, the space heating and hot water demand is the biggest proportion of overall energy use (c.80%). With the current \u2018spark gap\u2019, simply flipping a home\u2019s fuel from gas to electricity will increase the bills by 4x. Ouch.<\/span><\/p>\n

If that home has as efficient heat pump installed with a SCOP (Seasonal Coefficient of Performance) of 4 (= 400% efficient) then this levels it out again. Phew. But fundamentally the heat demand is still the same and the heat pump must produce a lot of energy to balance the scales from heat losses. <\/span><\/p>\n

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Devon CC Retrofit Guide<\/span><\/a> Typical end use data for a UK home in 2021.
(Source: Energy Consumption in the UK (ECUK) data from BEIS)<\/span><\/em><\/p>\n

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Using Fabric First to get a home heat pump ready and eventually, fossil fuel free. Chapter 2 Architects.<\/span><\/i><\/p>\n

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This is where <\/span>Fabric First<\/i><\/b> comes in: by increasing the performance of the building fabric, the heat we put in stays in, meaning fewer losses, reducing the energy demand.<\/span><\/p>\n

The home\u2019s next boiler or heat pump is smaller as it is required to cover a smaller heat balance deficit.<\/span><\/p>\n

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Fabric First<\/h2>\n

[\/et_pb_text][et_pb_text admin_label=”Fabric First” _builder_version=”4.27.4″ _module_preset=”default” custom_padding=”||||false|false” global_colors_info=”{}”]<\/p>\n

Fabric First is the best practice approach to Whole House retrofit that underpins PAS 2035, the UK government\u2019s retrofit standard. In practice, this encourages insulation measures before technology, so loft insulation, cavity wall insulation and better windows are prioritised over solar PV and heat pump technology. PAS 2035 section 5.5 states:<\/span><\/p>\n

\u201cThe existing building fabric should be as energy efficient as possible before spending resources on other measures. Subsequently, because insulation measures are generally among the most cost-effective and long\u2011lasting, and thus the best investment, insulation is usually the most appropriate next step. Insulating the fabric first also reduces the required capacity and cost of the heating system.\u201d<\/span><\/i><\/p>\n

Fabric First uses a 5-stage process, summarised as:<\/span><\/p>\n

1)<\/span> \u00a0 \u00a0 \u00a0 \u00a0 <\/span>Undertake necessary repairs so you progress from a sound base,<\/span><\/p>\n

2)<\/span> \u00a0 \u00a0 \u00a0 \u00a0 <\/span>Implement \u2018low hanging fruit\u2019 like energy efficient lightbulbs,<\/span><\/p>\n

3)<\/span> \u00a0 \u00a0 \u00a0 \u00a0 <\/span>Use insulation upgrades to the fabric to improve thermal and airtightness values,<\/span><\/p>\n

4)<\/span> \u00a0 \u00a0 \u00a0 \u00a0 <\/span>Hit the heating demand as efficiently as possible (which could include smart controls),<\/span><\/p>\n

5)<\/span> \u00a0 \u00a0 \u00a0 \u00a0 <\/span>Use low or zero carbon technology like solar PV or heat pumps, but as a top-up on existing performance.<\/span><\/p>\n

Note, this process should not be followed at all costs, and PAS 2035 recognises the need to say, replace a distressed heating systems or the constraints imposed by heritage.\u00a0<\/span><\/p>\n

Step 3 could be in multiple phases, so uses incremental improvements to the building’s insulation & airtightness reduces the heating demand before switching from cheaper gas to an electric heat pump. These steps are aiming to get the home \u2018heat pump ready\u2019 so there are fewer barriers and less physical disruption to installing a heat pump in the future.\u00a0<\/span><\/p>\n

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LETI Climate Emergency Retrofit Guide Fig. 5.1 Whole House Approach<\/span><\/i><\/p>\n

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The main thing counting against Fabric First is the low starting point of UK housing. If it takes 10 phases to get a home ready for a heat pump, that\u2019s not only a passion-killer, but maybe means 5-10 more years pumping out carbon emissions from fossil fuels. Meanwhile, there\u2019s still a skills shortage to deliver these millions of insulation upgrades and lack of finance options for private homeowners and landlords. <\/span><\/p>\n

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Fabric Fifth?<\/h2>\n

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Nigel Banks, <\/span>Technical Director \u2013 Low Bills and Zero Carbon<\/span><\/i> at Octopus Energy provoked a few rounds of social media fisticuffs in 2023 when he dared to stand up and speak quite loudly in the retrofit quiet carriage. He said if saving carbon was the goal here, maybe we should start with the heat pump and follow on with the fabric measures: hence the birth of Fabric Fifth as an alternative strategy.<\/span><\/p>\n

Nigel\u2019s 5-stage manifesto can also be summarised as:<\/span><\/p>\n

1)<\/span> \u00a0 \u00a0 \u00a0 \u00a0 <\/span>Install a heat pump using the BUS grant to vastly reduce emissions on day one,<\/span><\/p>\n

2)<\/span> \u00a0 \u00a0 \u00a0 \u00a0 <\/span>Install a Smart Meter, Smart Controls and Smart Tariff to avoid peak charges and smooth off the effects of the \u2018spark gap\u2019 through efficient use of energy,<\/span><\/p>\n

3)<\/span> \u00a0 \u00a0 \u00a0 \u00a0 <\/span>Increase comfort with draught proofing and simple energy saving tips,<\/span><\/p>\n

4)<\/span> \u00a0 \u00a0 \u00a0 \u00a0 <\/span>Invest in solar PV and battery storage to support the all-electric home,<\/span><\/p>\n

5)<\/span> \u00a0 \u00a0 \u00a0 \u00a0 <\/span>Major fabric insulation upgrades to walls, floors, roof, windows etc.<\/span><\/p>\n

You\u2019ll note that stage 3 is similar to Fabric First\u2019s stage 2 \u2018low hanging fruit\u2019, and the major fabric upgrades are implemented last. Given how disruptive and costly these measures can be, it does beg the question <\/span>will these things ever happen?<\/span><\/i><\/p>\n

Explaining the early implementation challenges, Fabric Fifth suggests before the home is insulated enough for the best performing 400% heat pumps, they could run on higher temperature, lower efficiency heat pumps that are still all-electric and bring significant carbon savings over a gas boiler. Nigel\u2019s article certainly did its job – to challenge the status quo.<\/span><\/p>\n

Both these approaches assume you are in control, but what if your boiler breaks on Christmas Eve?<\/span><\/p>\n

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Proactive Planning<\/h2>\n

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A key part of the decision making is also the age of your current boiler and how close to end of life it is. Hopefully, the remaining years can be used to prepare the home for its next low carbon heating source. Encouraging heat pump surveys now is a good way to establish what each home\u2019s challenges are so homeowners can work towards being heat pump ready when they want to make the switch. This can also spread the cost.<\/span><\/p>\n

If your current boiler dies before the home is ready, the path of least resistance is probably a new gas boiler, tying the home into 10 more years of high emissions. At a recent panel discussion about heat pump uptake at Futurebuild 2025, Kestrix CEO Lucy Lyons talked about \u2018creating a funeral plan for your boiler\u2019, which is an elegant way to describe how we must change our central heating purchases from reactive to proactive ones.\u00a0<\/span><\/p>\n

Your future heat pump needs planning and preparation. If running a combi, you\u2019ll need space for a tank. If the radiators are small, they\u2019ll likely need increasing in size to deliver the lower temperature heat over a larger surface area. If you\u2019re putting gas-powered underfloor heating in the kitchen now, size it for a heat pump. Future proof every upgrade you make from this point forward.<\/span><\/p>\n

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Diagram of the components for a heat pump central heating system.
<\/span>(Source: Samsung Product Catalogue)<\/span><\/em><\/p>\n

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Easy Wins<\/h2>\n

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Returning to the question of <\/span>how much is enough<\/span><\/i>, we can agree all sides are advocating for some fabric measures alongside the initial heat pump install (not forgetting good ventilation too). It just makes good sense to give the heat pump the best chance of success. These \u2018easy wins\u2019 or \u2018low hanging fruit\u2019 are often DIY tasks that are cheap to install and avoid the need for external contractors like:<\/span><\/p>\n