Fabric First and Refurbishment Excellence Knowledge and Skills for a Low-Carbon UK Lynne Sullivan OBE
Background:Objectives:• Climate Change Act requires 80% cut in CO2 for 2050 (when an estimated75% of existing buildings will still be in use)• The European Parliament is currently negotiating texts pertaining to the building renovations element of the Energy Efficiency Directive...Mechanisms:•Green Deal demands “an Existing Homes Hub... To share the latest research on energyefficiency” and provides a finance mechanism repaid through energy bills•Part L consultation calls for energy demand standards (kWh/m2) to apply to extensions to existingbuildings; as well as Consequential Improvements.. (?)Issues:•European Parliament text suggests 75% energy reduction ~ “deep” renovation – of public bodies’buildings...•A comparison of Energy Efficiency Programmes for Existing Homes in 11 countries (RAP forDECC 2010) suggests a single-measure approach may create substantial technical barriers as wellas higher overall costs if ‘deep, comprehensive’ refurb is what is required to achieve climate goals
Relevance of CORE research:Setting a clear trajectory to cost-effectively cut carbon from existing buildings (ref Article 3a ofEuropean Parliament text on EED):-A national renovation plan to be published (by Jan 2014?) to meet 8)% reduction in energy useacross the whole existing building stock by 2050- Annual targets for staged reductions on the way to ‘deep’ refurbishment- CORE research recommends establishing a process to support refurbishment interventionsdesigned around the specific requirements of an individual property:• Pattern book approach – housetypes / building element criteria• Decision matrices identifying type, criteria, key elements etc•Engagement with major players and pilots, evaluating lessons learned•Engagement with education and training, and professional institutions for skills•Engagement with manufacturers re capacity and innovation
Example of ‘Holistic’ Approach:Sustainable Traditional Buildings Alliance calls for a ‘systemic’ approach ie a holistic approachconsidering interactions rather than an approach based upon individual measures, buildingelements or technologies, for traditional buildingsShowed the shortcomings of the Glaser method of hygrothermal assessment which assumes thatall moisture comes from the room, that construction moisture has dried out and thatdriving rain, freeze-taw events don’t happen (ex Joseph Little’s Building Life Consultancy) Illustration from Joseph Little’s Building Life Consultancy
Example of ‘Holistic’ Approach:The SBTA ‘systemic’ approach inter alia highlights the need for greater understanding of the effecton human health of retrofit, and concern that ventilation and indoor air quality are not linked in theGreen Deal to other measures such as fabric insulation and draughtproofing which may requirechanged ventilation.The findings of a recent research study undertaken by Zero Carbon Hub and NHBC Foundationare, therefore, also relevant to retrofit
Example of ‘Holistic’ Approach:The Greater Manchester housing retrofit programme aims to improve the energy efficiency of thehousing stock and educate residents on how they can reduce their energy consumption to savecarbon and reduce their fuel bills. A Greater Manchester Low Carbon Housing Retrofit Strategy iscurrently being produced that encompasses this work and sets out GM’s ambition to deliver 48%reduction in carbon emissions from the housing sector by 2020: 7 years ahead of the nationaltarget. This strategy is currently out to consultation and the final version is imminent Illustration from Carbon Co-op; Urbed
Example of ‘Holistic’ Approach:DECC’s Local Energy Assessment Fund has supported several organisations in Manchester toundertake pilot studies of home energy, assessing the current condition and energy use of thedwellings and produce a range of bespoke behavioural and retrofit options to reduce energy use,carbon emissions and fuel bills.•Action for Sustainable Living (with Ecospheric) are developing assessment methodologies usingthermal imaging and moisture mapping•Carbon Co-op (with Urbed) and developing a whole house survey based on EPC but moredetailed, taking into account occupancy patterns and behaviour.Green Deal finance in this context (with its Golden Rule payback requirements) looks notuniversally relevant, and could tackle only the ‘low-hanging fruit’ rather than a stepped approach towhole house retrofit. Alternative funding mechanism? Eg Carbon Re-Investment Society providing long-term finance, low interest rates, and cross subsidy from FIT etc
Alternative Funding Mechanisms:• Carbon Re-Investment Society• Retrofit Revolving Guarantee Fund (Radian)The RRGF is a sustainable and affordable finance model developed in Europe to levels where 2%of national housing stock is refurbished to advanced energy efficiency standards annually,following the introduction of the RRGF principle by the World Bank and IFC.-Borrowing for retrofit takes place against a guarantee fund (at lower interest rates). The fundearns interest which pays for the financial management cost of the programme- Borrowing can take place at a community level- Programme management has a strong social dimension, engaging residents- Residents benefit from a ‘Pay as You Save’ approach, whereby low monthly repayments are lessthan their overall annual running cost savings post retrofit. This could be paid as a service chargeor an increase in rent. The loan remains assigned to the property....supposedly can accommodate, and work in a complementary way, to FIT, RHI and Green Deal
Alternative Funding Mechanisms:Across Europe, it is estimated that 8 trillion Euros are needed to upgrade European existing stock.•KfW in GermanyThe German scheme offers up to 70,000 Euro for home energy efficiency improvements at interestrates which reduce according to how much energy you are savingThe cost of the scheme is more than paid for from VAT and tax returns as well as creating thebenefits of new jobs which reduce unemployment benefit burden• 0% loans in FranceEnergy efficiency improvements in France can be funded by loans at 0% interest rate
Worked example of the sequential approach:Sustainable BY Design have been collaborating on a study to identify appropriate targets for a1960s tower block refurbishment aiming to improve energy efficiency of the building fabric, takinginto account:- Appropriate assessment methodologies- Impacts of different measures- Practicalities bearing in mind: finance, resident impacts etc • We decided to model the existing and proposed improvements using Passivhaus Planning Package which would be used along with thermal bridging calculations and future air pressure testing, against the Enerphit standard, as we considered this to be the leading edge of fabric efficiency for existing buildings, administered by the Passivhaus Institute in Germany, and proven to deliver through measured performance in use- With an EnerPHit refurbishment, up to 80% heating cost savings per flat should be realisable: Existing space > 200kWh/m2 pa ~ £800 pa equivalent heating demand Proposed heating < 25kWh/m2 pa ~ £100 pa equivalent demand (Enerphit)
Worked example of the sequential approach:Using Passivhaus Planning Package, we had the flexibility to model a whole building block, asdistinct from the SAP individual dwelling calculation.Measures considered included:•Elevations / wall construction•Balconies•Ground Floor Construction•Roof construction•Windows / doors•Ventilation•Heating•Air LeakageInitial analysis of the heat losses and how space heating compensates:
Worked example of the sequential approach:From the PHPP (where the Excel format allows sensitivity analysis of different interventions) thewindows and walls make up the largest heat loss – the existing U value of the wall is estimatedat approximately 1.9W/m2K. There are also significant thermal bridges formed by the floorslabs running continuously from inside to outside.For Wall upgrade, there are several options depending on phasing and finance:6.Cavity wall insulation only7. Internal insulation only or as well9. External Insulation with integrated finish.
Worked example of the sequential approach:Although cavity wall insulation can offer some improvement inthermal performance, the size of cavity and significantthermal bridging created by the externally exposed concretefloor slab negates the installation of cavity wall insulationalone.Therefore installation of external wall insulation isrecommended to wrap around the building to create a‘continuous’ thermal layer. In this case external wall insulationcoupled with cavity wall insulation - offer the potential toreduce the U-value to approximately 0.13W/m2 andeliminates the thermal cold bridging.This measure has implications for sequencing, as any newwindows need to sit within the insulation zone and packed(with insulation) below the existing slab level to minimise thecold bridging..
Worked example of the sequential approach:Putting in new windows is a major contributor to improved comfort conditions, as even the partialreplacement windows have not stopped draughts entering the building around the structuralconcrete frame.This has a major implication on sequencing, but if staged refurbishment is vital, then better to put thewindows in first as far out to the external face as possible, and insulate the cavity. Then,subsequently, fully insulate externally. (Note: taking out the windows exposes the cavity forinspection in any case, and these elements can substantially improve air tightness).
Worked example of the sequential approach:Roof construction - similar to the typical floor section, again there is no insulation above or belowthe roof slab, therefore the thermal performance or U-value of the construction is poor compared tocurrent building regulations. There is also a significant thermal bridge formed by the roof slab andparapet.Externally insulating the flat roof construction and around the parapet could improve the U-value toapproximately 0.14W/m2K while also providing the opportunity to carry out maintenance andfurther weather proofing the roof structure – is relatively easy to carry out independently.
Enerphit Verification: The relative improvements of the losses and the need for compensating gains is illustrated – the space heating load can be mainly provided by an MVHR system, although Hot Water demand is still present and minimal top-up radiator can be run off that system.
Practicalities of the Stepped Approach : The intermittent and irregular release of funds by the Local Authority will be the greatest barrier to achieving an integrated, successful retrofit to a holistic building, all-encompassing, energy efficient standard like Passivhaus EnerPHit. • Ideally, the external walls/floor/roof insulation upgrade and window replacement should be completed in one construction phase achieving the best use using of full height, safe scaffolding access. In that way the junctions between the external wall insulation and the window frames replacement can be resolved together. • Installing the window upgrade first would locate the frame in the wrong place relative to the external insulation to follow, but would be advantageous (and is urgent for the residents) in dealing with current drafts and window condensation. •Only blowing insulation into the cavity of the external wall would provide some thermal benefit to the residents, but may, pending further study, exacerbate any damp problems that currently exist within the external fabric. • It would be prudent to allow for a condition survey of the existing concrete structure, taking advantage of opening up the construction as part of the retrofit works.
Practical Approach to Phased ‘deep’ RefurbPhase 0Existing Construction: >200kWh/(m2.yr)a. No insulation within external fabricb. Poor performing steel framed, single-glazed windows – some UPVC double-glazed upgradec. Continuous communal extract ventilationd. New gas combi-boiler individual flat heatinge. Poor fabric air tightness >15 m3/h/mPhase 1.Insulate cavity wall, flat roof and Replace single glazing: ~150 kWh/m2 paa. Cavity wall insulation only.b. Upgrade all steel-framed single-glazing to thermally broken, composite-framed triple glazing.c. Upgrade roof insulation.d. Air tightness upgrade at window junctions.<10 m3/h/mPhase 2.Insulate external wall, ground floor: ~100 kWh/m2 paa. External Wall Insulation (EWI) Render Systemb. Ground Floor upgrade with EWIc. Roof Upgrade with EWI to parapetd. Option to glaze and enclose Balconiese. Air tightness upgrade at window/wall/roof/floor junctions. <5 m3/h/m Phase 3.Replace double glazing and install MVHR ventilation system: ~25 kWh/m2 paa. Upgrade all UPVC double-glazing to thermally broken, composite-framed triple glazing.b. Air tightness upgrade at window/wall/roof/floor junctions. <2 m3/h/mc. Replace communal extract ventilation with individual flat MVHR system