June 2017: The Art of the Possible

The Art of the Possible

On the hottest day of the year so far, we’ve been debating the relative merits of underfloor vs radiator heating.

Back in January, none of us thought there was anything unusual about wearing coats (and even gloves and scarves) for the blessing carried out in the Lady Chapel before we handed the building to our conservation builders.  The Lady Chapel is a beautiful space (that almost goes without saying).  But it’s also very cold.  Despite the fact that it’s on a smaller scale than the Norman nave, that doesn’t stop it from having an extraordinarily high ceiling.  And the beautiful glazing (a mix of medieval stained glass in the east window alongside much more recent Arts & Crafts works by Christopher Whall to the north and south) means that any heat which doesn’t rush to the top of the building, is lost thanks to the poor insulating properties of glass.

You can see why the idea of underfloor heating is so appealing.  We have to lift the tiles and ledger stones which cover the floor of the Lady Chapel anyway: we need to remove the layer of Victorian concrete which sits beneath them and is a key reason for the damp atmosphere within the space.  And if we have to do that, why wouldn’t we take the opportunity to install a heating system which is both effectively invisible and which is also exactly where we want it to be in terms of the comfort of our visitors?  The technical term which is bandied about is “thermal comfort” and in this instance it means we can handle a slightly lower overall temperature because the part of the building occupied by people (the floor) is continuously kept toasty warm thanks to the underfloor heating.  

As with all elements in Pilgrim, we’ve prepared as well as we can, spending over three years employing experts to monitor conditions in the space, to research and work through options, to carry out trials and tests, to seek the necessary approvals and of course to work out the costs and ensure we have money in the bank.  We’ve always known the process would be tricky and I’ve personally been somewhat awestruck both by the level of technical knowledge brought to bear in modelling different heating options and by the care our building team have shown in lifting the hundreds of medieval tiles at the west end of the Lady Chapel.  

Despite our careful preparations, we have always known that we might need to re-think our plans.  Earlier this week we concluded that there are three areas which aren’t suitable for underfloor heating: there are two smaller areas where the “cementitious substance” used to bed down the tiles is so much stronger than the tiles themselves that we would only be able to lift the tiles in pieces.  The tiles were originally in the Quire and were moved to the Lady Chapel by our Victorian ancestors - who took a rather cavalier approach to keeping them in their original patterned layout.  These days we take a different view of our role as custodians of the building and won't be pursuing our original plans since the damage to these two areas would be so significant.  There’s also a larger area at the very west of the Chapel.  Here the issue isn’t lifting the tiles: they’ve come up beautifully and are neatly stacked into numbered trays which are in turn plotted on a colour coded floor plan.  It isn’t even the two (probably Norman) walls we’ve uncovered as the chapel joins the main Cathedral (that’s a throwaway line which will certainly result in emails!).  It’s the structure of the cathedral itself.  Underneath this part of the Lady Chapel is part of the Cathedral’s Crypt and the gap between the top of the Crypt and the Lady Chapel floor level is rather smaller than we’d thought - and certainly not large enough to accommodate the necessary underfloor heating gubbins.

Which brings us back to the hottest day of the year and a table of experts, pouring over different options to keep the space warm.  Eventually we agreed on Plan D.  And then we left to get on with extra homework: full recording of the newly discovered walls to assist discussions about pipe routes; modelling the impact of reduced underfloor heating; the addition of two larger radiators at the very west end of the cathedral; re-costing the whole system with one rather than two air source heat pumps; and lifting the first of the large ledger stones to see if any other areas are not what we’d thought.

As our plans change and evolve, there are lots of interested parties to keep up to speed.  We were fortunate that one of our key funders (the Summerfield Trust) had sent a representative to the meeting.  The following day, the Heritage Lottery Fund were on site and able to take a look for themselves.  Early next week I’m showing some of the Friends of Gloucester Cathedral around the space.  But in the meantime we need to catch up with the Cathedral’s own governance systems: the prosaically named Pilgrim Board and the rather more arcane Fabric Standing Committee and Fabric Advisory Committee.  

By the time we get to the coldest day of the year, work to the Lady Chapel will be finished.  Whether we end up with Plan D or E or F, the challenge is to keep the fabric in good condition, without damage or compromise and warm enough that coats and gloves are left off.  I’ll let you know how we get on!



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