Sustainability response

Sustainability: the Advisory Committee Response

 

This pilot offered the Council a significant opportunity to support and guide the burgeoning efforts of an increasingly inclusive community effort to enhance the Conservation Area by implementing appropriate energy saving measures.  The reverse has happened.  The Council has instead caused confusion, sapped confidence and stoked division.

At the outset positive models of the way forward were offered, for example, the Warmer Bath document.

Before the pilot got going the Council pre-empted the outcome in deciding a planning application on the following basis:

“I am aware that the use of render in conservation areas is a contentious issue, but where it is used for energy saving purposes we apply national guidance in the form of Planning Policy Guidance 5 (PPS5) which states that potentially negative effects on heritage assets should be weighed up against the public benefit of mitigating the effects of climate change. In this case we have to assess the importance of the heritage asset ie the rear of the building, as opposed to the roof or front elevation, and the potential harm ie alterations to the rear of a building where many of the neighbouring buildings have been altered at the rear.”

We absolutely agree that PPS5 is pivotal.  However, PPS5 does not say what the Council Officers say it says.  The relevant provision here is HE1.2

HE1.2     Where proposals that are promoted for their contribution to mitigating climate change have a potentially negative effect on heritage assets, local planning authorities should, prior to determination, and ideally during pre-application discussions, help the applicant to identify feasible solutions that deliver similar climate change mitigation but with less or no harm to the significance of the heritage asset and its setting.

To the extent that this application could be said to have been “promoted for their contribution to mitigating climate change” [1] the obligation imposed on the Planning Authority is to help the “applicant identify feasible solutions that deliver similar climate change mitigation but with less or no harm to the significance of the heritage asset and its setting”.

This pre-emption resulted in marked loss of enthusiasm for the pilot and two unrepresentative and abysmally attended ‘working party’ meetings.  The rush to get something out in time for the ‘Green Deal’ launch precluded efforts to repair the damage done. [2]

This, in lawyers’ speak, fundamental ‘misdirection’ as to the Council’s obligations and the proper approach is not only the poison at the heart of the current proposal document but will also underpin the borough wide guidance.

PPS5 has now been  replaced but, as English Heritage guidance points out, thanks to a massive national campaign, its substance is intact.

We cannot simply consume our way out of the global energy crisis. [3]   Careless and inappropriate consumption has played a large part in getting us into the mess we are in.  Serious change requires significant lifestyle changes and a real understanding of our homes and how we use them.

Dartmouth Park Transition recently organised a viewing of the film ‘Utopias’.  A speaker is filmed putting the matter succinctly:

“We are recognising that corporations have stolen a lot of the agenda around climate chaos.  That it is still their power in the media that is driving a lot of the discourse and that we as ordinary people need to take the discussion the debate the answers and the solutions back.”

Sadly, what could have been a ground breaking opportunity to enhance the Conservation Area by helping the community to deliver affordable comfort in more energy efficient homes for all residents has been hijacked and turned into a damaging and thinly veiled merchandising effort for the Government’s absolutely pernicious ‘Green Deal’. [4]

The ‘Green Deal’ and its sister ECO project together constitute perhaps the most complete example to date of the Government’s attempts to ‘roll back the State’.  The intention is to displace the main responsibility for reducing carbon emissions from Government to individual households.  In marked contrast to almost everywhere else in Europe, not a penny of our taxpayers’ money has been allocated to the scheme.

The ‘Green Deal’ is a scheme to “enable private firms to offer consumers energy efficiency improvements to their homes, community spaces and businesses at no upfront cost, and recoup payments through a charge on” future electricity bills.

In the cause of reducing Government debt millions are to be encouraged/guilt tripped/frightened into irresponsibility taking on huge amounts of costly private debt.  Irresponsible because the debt will attach to the electricity supply of the property rather than to the individual borrowing the money and because the borrowing is presented as no cost and risk free.  The Government will not even lend its much vaunted ability to borrow money cheaply to the scheme.

As George Monbiot, green economist and journalist, points out in, for example, his blog article: ‘The green deal is useless, middle-class subsidy’; perhaps the most offensive aspect of the schemes is that all money not raised from costly private borrowing is being raised from increasing electricity prices.  The poor, including particularly those already in acute fuel poverty, will pay massively disproportionately whilst the middle classes take much of what little benefit is to be had.

The Government intends to replace almost all public investment in energy supply, for example, on a new generation of nuclear power stations, with increases in electricity prices to the particular detriment of the poor.  These increases, taken with the removal of the obligation on Ofgem to regulate consumer prices, is, perversely, the stick being used to try to frighten the middle classes into participation in the schemes.

In short, the ‘Green Deal’ package is another example of what the Archbishop of Canterbury, Rowan Williams, describes as a “deeply damaging withdrawal of the State from its responsibilities to the most vulnerable”.

As Sam Arie [5], academic economist and journalist, said in The Ecologist last November

“We have been living from bubble to bubble. First the dot com bubble, then the housing bubble, and you could hardly have missed the Southern European bond market bubble. It is as if we are in constant search of a new folly in which to lose our heads – and then our shirts. But if anyone has been wondering where the next bubble will come from, we have the answer: it will be an energy bubble.”

One has to look at the small print of this so-called ‘Green Deal’ to understand the mechanism which virtually everyone agrees will produce one of the greatest miss-selling scandals since the Thatcher era, to say nothing of the many banking scandals.

Within the ‘Green Deal’ much is made of a ‘golden rule’ said to ensure that the repayment of the debt will only come from cost savings one makes during the life of the product.

First, it is a nonsense to believe anyone will be willing to go through the trauma of, for example, installing solar water heating or photovoltaic panels, for only the satisfaction of knowing that one has, at best, made an absolutely infinitesimal contribution to helping the Government meet its carbon reduction targets.  Anyone entering such an arrangement will expect and be promised significant savings over and above those required to pay off the debt before the equipment has to be replaced. 

More significant, the actual commitment isn’t to no-cost borrowing.  The commitment is  to payment not against what you actually save but  against what some minimally trained operative, probably with a vested interest, predicts/expects you will save, a very different kettle of fish.

To return to Sam Arie’s article [6]

“And that is exactly what the Green Deal is – a clever marketing strategy. As such it will no doubt be successful in the short run, generating euphoria and new lending in equal measure as the bubble in home energy services starts to build up. This phase may last for a few years, but eventually the poor quality of investments will start to show through, millions of households will find they are in negative equity on their Green Deal plans, and they will start failing – or refusing – to make repayments. The government will discover the fundamental truth that you cannot make an unattractive investment into an attractive one simply by refinancing the cash flows. There will be an outcry, the energy bubble of – let’s say – 2016 will burst, and widespread losses will be incurred.”

We rather doubt the ‘Green Deal’ will be that successful  even in the short term.

 

None of this will come as the least surprise to Camden Council.  When it was suggested that the Council should become a Green Deal Provider it baulked at the prospect, fearful it would be tarred with the mis-selling brush and face consequent public opprobrium.

That the Council should now wish to open a back door to that opprobrium simply beggars belief.

Indeed, one of the inducements offered to the Advisory Committee for agreeing to participate in this exercise was that what was produced would try to arm Dartmouth Park residents and help them to protect themselves from the worst excesses of the ‘Green Deal’.  The reverse is happening.

Asked why this U-turn, they have answered to a person,  “becausethe Green Deal is the only game in town”.  That, frankly, is nonsense.  Since, in the absence of any serious public expenditure, it is the residents of Dartmouth Park who, broadly speaking, will pay for whatever is done, it is they and they alone who will decide what, if anything, they are prepared to buy into.

It is important to remind ourselves that the ‘Green Deal’ isn’t about identifying the most effective, cost effective and appropriate energy saving measures available, let alone the most effective, cost effective and appropriate measures in relation to a Conservation Area.  It is about TESCO or B &Q or whoever deciding what energy efficiency ‘improvement’ products they can profitably [7] sell within the parameters of the ‘Green Deal’.  The requirements of the ‘Green Deal’, particularly the ‘golden rule’, require mass production focussed on the cheapest possible version (the words cheap and nasty come to mind) of any product combined within a non-complex installation environment.  However effective, low or no cost measures won’t feature in the ‘Green deal’.  The contrary, highly effective low or no cost measures are typically seen as undermining potential sales unless they too can be turned into a sales opportunity. [8]

Given all this it was inevitable that the ‘Green Deal’ would be heavily centred on external insulation.  Major energy savings from incidental improved airtightness to a building are used to boost predicted savings from dropping a 120 to 150mm blanket over all external walls obliterating all pre-existing character and historic features.

The incontestable reality is that one cannot possibly reconcile dropping a 120 to 150 mm insulation blanket over all the exterior walls of a ‘heritage asset’ in a Conservation Area and obliterating all of its features with the statutory duty to preserve and enhance those assets.  Basically, external insulation is simply not an appropriate means of achieving energy efficiency improvements within a Conservation Area.

The central failing here is that the whole document is underpinned by a mistaken acceptance of the untenable proposition that, conservation considerations apart, consuming external insulation products is the only ‘serious’ available way forward.  This acceptance, which is shared by a small number of individuals within our community, has set up an unnecessary and damaging conflict which presents the need to preserve and enhance our heritage as an obstruction to the greening of the Conservation Area.

The result has been a sterile debate obsessively centred on the cheapest and least appropriate (and nastiest) forms of external insulation.  Some have pressed for allowing rendered external insulation on an even greater number of walls than is already suggested.  It goes without saying that, the fundamental misdirection apart, what is being proposed already goes way beyond what is acceptable or is compatible with the Council’s statutory duty to preserve and enhance the Conservation Area.

No one will be satisfied with the outcome wherever the line is drawn.  We will continue to resist this notion of the Conservation Area as a sort of film set where only the street façade is seen as important.  It has long been accepted that most of the side and rear elevations, particularly those that be seen both from the public realm and large numbers of neighbouring houses, are critical to the preservation of the character of the Conservation Area, particularly, because of its geography etc, the Dartmouth Park Conservation Area.

The harm which will be done can’t possibly produce a commensurate gain in terms of reduced carbon emissions.

As the main text is at great pains to point out, partial external insulation is hugely and disproportionately less effective.

It is highly improbable that partial external insulation could ever meet the financing from savings test of the ‘Green Deal’.  Fortunately the complex planning and building environment which results from the eventual guidance will discourage any real interest from major ‘Green Deal’ providers.

The reduced effectiveness of partial external insulation apart, eliminating the incidental savings from improved airtightness by a low or no cost programme of improvements, starting with effective draught proofing, makes self-financing external insulation a very difficult sell in London’s increasingly mild climate.  Add other modest low cost physical and life style changes, for example, shutting off a conservatory from the main accommodation when it is cold,  then making a case for self-financing external insulation is pretty near impossible.

As important, this sort of bitty external insulation will only have relatively modest impact on securing either significantly improved energy efficiency or reduced carbon emissions.  As is confirmed by the draft document, if you can get through the long winded and impenetrable stuff about cold bridges etc., heat doesn’t sit patiently waiting to pass through the bit of wall you happen to have insulated.

Addressing the Council’s other misplaced obsession, comprehensive retrofitting of heritage homes, it may be that  there will be handful of people living in the Conservation Area who over, say, the next ten years wish to undertake a major refurbishment of their homes including the hugely costly and complex mix of internal and external insulation which the document explains would be necessary to produce real results at this level.  You don’t need a dedicated elaborate planning guidance document in order to deal with such cases.

Thus, for example, it is suggested in the draft proposals that the central areas of the flank walls of the pairs and groups of houses in Dartmouth Park Road (west) could be insulated externally without doing grievous injury to the character of the houses or the Conservation Area.  It is, of course, accepted that any such insulation would have to be set well back from the corners in order to avoid conflict with the key architectural features of the houses and in order to avoid the pairs of houses becoming visually imbalanced/lopsided.  The flank walls of the pairs are approaching three metres apart and are visible for the whole depth of the houses.  The walls are brick, mostly London stock.  The draft guidance appears to suggest that rendered insulation would be acceptable.  It plainly isn’t but assuming this is an error and that it is intended that the guidance will specify a finish of cut slips of reclaimed London Stock bricks, it may be true that the impact on the relatively well preserved houses or the Conservation Area wouldn’t be catastrophic.

What is clear is that the benefits of undertaking what would be very costly works would be pretty marginal and barely noticeable.  It is certainly clear, particularly where there have been no or low cost improvements internally, that one couldn’t begin to recover the cost of such works, even if the external insulation was finished with render, from savings even taken over a fifty year period even assuming nothing goes wrong.

Turning briefly to solar water heating and PV panels on roofs, we do admit to some surprise at the over the top advocacy by some ‘greens’ in favour of allowing the cheapest and most intrusive types of panel on roofs which are visible to large numbers of people.  Most ‘greens’ are rightly dismissive of this sort gadgetry as ‘eco-bling’ [9].  There is absolutely no case in terms of making a material reduction in carbon emissions for any derogation from the Council’s legal obligation to preserve and enhance the Conservation Area.  It will come as no surprise that litigation about mis-selling  of such panels has already reached sufficiently high volumes to attract ‘ambulance’ chasers.

Panels can, of course, be more or less intrusive.  Panels set completely flush into a roof are significantly less intrusive than panels sitting 50 to 100mm above it.  Sadly, even if such a distinction was adequately drawn in the guidance, it would certainly be ignored.  Camden’s guidance on roof windows has long specified that they should be flush with the roof but this requirement has been almost universally ignored by the planners.

In stark contrast to the promotion of ‘eco-bling’ gadgets, it is absolutely typical of the draft proposals that the main text entirely fails to deal with what is called biomass heating.  A goodly number of Dartmouth Park residents have, for example, installed highly efficient wood etc burning stoves.  In addition to the considerable benefit in terms of enhanced comfort, biomass heating can make a significant contribution to reducing carbon emissions.  (The Council Officers probably don’t know about this because, in the rush to get the document out before the launch of the ‘Green Deal’ and because the pilot was absurdly underfunded, they declined to look at any of the actual buildings in the Conservation Area let alone consider the efforts local residents have already made.  Instead, they have relied on absurdly gross generalisations about the characteristics of all pre-1930s buildings which rubbish both the efforts of local residents and the buildings they live in.)

In this context it would be wrong to pass over the issue of ‘lobbies’.  In the both the ‘survey’ and during the somewhat bizarre Council organised walkabouts it was urged that any house with a front door which is set back from the main building should be enclosed to form a lobby.  Lobbies are probably the most researched issue in energy conservation.  As a goodly number of Dartmouth Park residents can confirm, from their experience of creating adequate lobbies within their entrance halls etc, lobbies can play an important part in securing the airtightness of their homes.  However, to be effective, one needs to be able to both open and close one door, after taking oneself through together with shopping, baby-buggies et al , before the second door is opened.  As the main text suggests, instead of creating a silly and pretty useless lobby and doing really serious harm to the appearance of, particularly, terraces, it would be hugely more cost effective to introduce an energy efficient door.

Does any of this matter? 

Sadly, it matters very much.

First, efforts at preserving and enhancing a Conservation Area are easily derailed.  One apparently minor but ill-judged act can seriously damage the appearance of a whole terrace.  We don’t need to wait for external insulation to demonstrate this.  Years of failed enforcement, poor decisions by planners and, most particularly, the Council’s failure to make Article 4 Directions in most of its Conservation Areas, have left scars everywhere.  (A very belated programme of introducing such Directives fell as part of the cuts after only a handful of Directions were made.)   For example, one can’t walk through any area of the Dartmouth Park Conservation Area without seeing an otherwise well preserved terrace scarred by a single house where the bricks have been painted or, worse, rendered and then painted.  This is true of highly visible front, rear and flank elevations.  In addition there are always a few unscrupulous developers who are happy to throw in a bit of eco-bling or whatever to try to improve their chances of getting otherwise unacceptable proposals through.

It will be open season on any elevation thus declared to be of low importance.

Second, it is a huge turn-off for the huge majority of the residents of the Conservation Area not least because, for example, external insulation, eco-bling products, whatever simply aren’t remotely relevant to, for example, the tenants and leaseholders of Council and other social housing.  Whatever other benefits might be claimed to arise from allowing more external insulation or whatever, none of this is even vaguely relevant to the urgent task of addressing fuel poverty within Dartmouth Park and it is, frankly, dishonest to suggest it is.

Finally, and most important, far from advancing the cause of greening the Conservation Area, the divisions stirred up by this process have been hugely counter-productive and have set back the cause for, very possibly, years.  It is now well settled (see, for example, the excellent study by the Energy Savings Trust) [10] that the only effective way to achieve progress is from the bottom up.  Neighbours who find that others within their community have successfully implemented unproblematic improvements which address issues which they too face, (initially most typically, draughts) develop the confidence to take action and are able to benefit from following in the footsteps of others.  People are able to learn from the experience of others where the pitfalls are and to avoid them.  Dartmouth Park is remarkably socially cohesive and particularly fertile ground for this sort of approach, or was until the Council blundered in.  Throughout the Conservation Area the spread of improvements which have proved successful had been escalating, notably, for example, renovation of window sashes by making them draught-proof and, in many cases, replacing single glazing with double glazing units.  The launch of the ‘survey’, which was exclusively focussed on the ‘Green Deal’, the products associated with it like external insulation and, indeed, anything and everything likely to impact negatively on the task of preserving and enhancing the Conservation Area, had an obvious and immediate dampening effect on these local initiatives.  The position was considerably worsened when the Green Party started campaigning for particular outcomes from the survey.  At least one initiative of a group of residents in a street was ‘deferred’ because some of the group lost confidence that they were doing the right thing.  The intention had been to bring in a contractor to undertake air pressure tests on at least four similar houses which would help to better identify the sources of draughts, leakage of warm air and generally measure the air tightness.

Interestingly, notwithstanding the Green Party’s campaigning and, more important, the absence of any non-intrusive options, for example internal insulation as against the external variety, the majority of those responding were remarkably resistant to measures which they thought might do injury to the character of the Conservation Area.  See Appendix B.

The draft proposals themselves have had remarkably little additional impact probably because most of the very small number who have tried to read them lost the will to live well before they got to the end.  Thoughtless Green Party campaigning has, though, maintained the negative impact.

That said, the thrust of the document is somewhat dismissive of no and low cost, minimal disruption approaches which are accessible to all the residents of the Conservation Area. [11]

More significantly, the document exaggerates the difficulties of using, for example, internal insulation.   Reading the document one might be forgiven for assuming that if the internal insulation isn’t 100mm thick it is pretty useless.  This is very far from the truth.  The reality is that one gets rapidly diminishing returns from increasing the thickness of insulation.  A goodly number of the houses in the Conservation Area have mostly [12] 13” brick walls plastered internally (as opposed to the 9” walls used to found the claims about the performance of our homes).   Without insulation the U-VALUE (Wm2/K) of the 13” wall is about 1.63. [13]  Add, say, 40mm of Phenolic foam [14] (to achieve, roughly, the equivalent of a filled cavity) and the theoretical thermal efficiency of the wall is improved by around 76%.  Increasing the thickness of the foam by 50% would only improve the theoretical thermal efficiency by a further 7%.  This is equally true of ‘healthier’ but less effective insulators or ultra-effective [15] aerogel products which can achieve filled-cavity equivalent with an insulation thickness of between 16 and 20mm. [16]

The draft document is overly preoccupied with and over-emphasises the importance of cold bridges et al.  This sort of stuff is of interest to a handful of people who may wish to produce ‘superhomes’ over the next ten years.  It would be a lot more pertinent to emphasise that the U-VALUE (Wm2/K) of a 13” wall of about 1.63 can be reduced to between 1.14 and 1.22 with a relatively cheap DIY/decorator level internal 10mm wall lining (or significantly better than that if one also used an 8mm aerogel blanket behind, for example, built in bookcases etc).

We don’t understand the continuing reservations expressed about window renovation.  It is usually possible to have real glazing bars with slim double glazing units.  Even if, in exceptional circumstances, it isn’t , ultra-thin (roughly 6.1mm) double glazed units with U-VALUEs (Wm2/K) of 1.4 or better have been used in Japan for decades. [17]  A variant using ‘crown’ glass has been used throughout Europe in ‘listed’ buildings for years.  The arrival of Pilkington’s ‘Spacia’ makes this technology readily available in the UK.  At 6.1mm the units are not much thicker than ordinary glass and it may even be possible to alter existing sashes which are in good condition to accommodate the units.  Until production levels increase such units are expensive but the cost is more than offset because one doesn’t have to replace the frames etc. [18]  A key task here is to warn residents against the very costly, very bulky Everest type replacement windows.

Finally, certainly as of now, we don’t have hoards of applicants beating down the doors of the Planning Department demanding to be allowed to drop a blanket of insulation over their homes.  The proposed guidance isn’t addressing any obvious need.

What we do have are significant numbers of applications for projects which will inevitably reduce the insulation potential of heritage buildings.

For example, much of the work of the Conservation Area is focussed on protecting rooflines from intrusive dormers, multiple roof lights, mansards, etc.  Most of the heritage roofs in the Conservation Area aren’t suitable [19] for the low cost ‘loft conversions’ and produce sub-standard accommodation.  These roofs are, though, perfect for highly cost effective insulation/improved airtightness works.   The ‘gruyere’ approach to roofs, punching several glazed holes in them, precludes such roofs from ever being able to meet the standard 270mm glass wool equivalent requirement.  The very best Velux conservation rooflight not only isn’t flush but has U-VALUE (Wm2/K) of 1.4 which is many times higher than is required for a properly insulated roof. [Meaning not clear: is the Velux insulation unnecessarily high, or is it too weak?] Typically, the need to ventilate the roof taken with the need to maximise head heights so that they at least approach minimum requirements, will leave only 50 to 60mm for insulation across the roof which is nowhere near what is required.  The combined impact of the Council’s failure to introduce the necessary Article 4 Direction and repeated grants of planning to bring all rooflights etc within planning control and delegated approvals is certainly outweighing the efforts of everyone trying to green the conservation area.  It is clearly unacceptable to have area specific guidance which entirely fails to address the only real challenge currently facing the planning system.

The present draft proposals are not in the right ballpark.  What we need is a document which helps applicants identify feasible solutions that deliver climate change mitigation with less or no harm to the significance of the heritage asset and its setting.  It is unacceptable to instead focus only on measures which are inherently harmful even if one then tries  half-heartedly to limit that harm.

 

 



[1]               It wasn’t, the applicants wanted to make a light open plan ground floor, including a new infill and compensate for the adverse effects by improving the only bit of external fabric left by partial external insulation.

[2]               Followed by an absolutely embarrassing ‘consultation’ meeting.  This in a community which regularly turns out meetings of between 50 and 100 residents.

[3]               The Council should know this better than after its experience of   its tenants setting the thermostat to the mid-twenties in its flagship retrofix house.

[4]               Very much akin to the food industry’s exploitation of people’s concerns about food and health by, for example, marketing sugar, salt and fat laden chocolate biscuits and cakes as contributing to one’s ‘five a day’ target on the basis of the inclusion of a few raisins.

[5]               Sam Arie is a Visiting Fellow at The Smith School of Enterprise & The Environment, Oxford University

[6]               The bulk of Arie’s excellent article is attached as Appendix A.

[7]               including, of course, the profits from selling credit.

[8]               Thus the consultation draft, for example, grudgingly admits no or low cost low intrusion minimal disturbance ‘air tightness’ measures can have very a significant impact but can’t then resist the temptation to immediately move onto high cost high disruption mechanical ventilation measures.

[9]              For example, Alexis Rowell, says “Energy efficiency is usually seen as boring…. (Private) energy generation, by contrast, is exciting because it’s about gadgets. But gadget-fixation can lead to classic mistakes, such as the installation of mini wind turbines on urban homes as David Cameron once tried to do – sometimes known as the ‘eco-bling’ approach to CO2 reduction:

 

“If [people] are putting costly photovoltaic cells, hot-water solar collectors and personal wind turbines on their becalmed, north-facing, turf-roofed, toxic timber-clad, non-airtight, poorly insulated houses, finished in high-emission materials – and they are sinking electricity powered heat pumps and rainwater filtration systems down deep holes filled with recycled concrete, next to their reed-bed gardens with a focal-point bird table – then they could, just possibly, be spending money more wisely.  The alternative to ‘eco-bling’, which is both cheaper and has much better green credentials, is ‘eco-minimalism’ – a good-housekeeping approach to ecological building design and specification, involving apparently on glaringly obvious strategies such as insulation, draught proofing and the use of healthy materials.”

Howard Liddell, Gaia Architects

[10]             Sadly, itself a victim of the ‘Green Deal’ having suffered massive cuts

[11]             Interestingly, it seems some ‘greens’ believe the little there is should be relegated

[12]             Less on the top floor and more around chimneys

[13]             Around 25% more thermally efficient than the 9” wall.

[14]             Plus straps, plasterboard etc

[15]             but, certainly until we see higher volume production, much more expensive

[16]             Plus straps, plasterboard, etc

[17]             These are vacuum rather than gas filled units.

[18]             Replacing sashes is a lot less disruptive because the onsite part of is completed in a few hours

[19]             because, for example, of the 30% pitch of most roofs

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