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The Church and its history


The village of Welwyn is near the site of a large Roman settlement around the ford which crosses the River Mimram on the road from Verulamium (St Albans) to Camolodunum (Colchester). There was probably a church building in Saxon times in Welwyn for, in 1986, archaeologists found Saxon Christian burials just north of the present building, but the first records of a church date from 1190. By c18 Welwyn had become an important posting location on the Great North Road with Dr Edward Young, the poet, as Rector. Throughout at least 900 years the Church of St Mary’s has remained at the centre of the village, which, unlike many other surrounding villages, has not moved during the period. During this time the church building has grown and evolved to meet the worshipping and social needs of the community as a whole.


The present church building, which is Grade II listed, is within the Welwyn Conservation Area just north of the modern crossing of the Mimram. It forms an attractive visual end to the High Street at the point where roads to the north and east diverge. The church is set in its churchyard, which has not been used for burials since 1882, bounded on the south and west by a hedge with gates and a c19 low brick wall and railings which are listed Grade II. The churchyard was extended eastwards in 1858 by the inclusion of Anchor Pightle, a small parcel of land previously occupied by the first school in Welwyn, founded by Dr. Edward Young in 1755.


The northerly part of the churchyard, with its historic memorials, is now the site of Church House, a new building constructed to the highest standards which provides meeting rooms, a kitchen and toilet facilities for the congregation and the community. Completed in February 2007 it was designed by Barry Roberts RIBA. The southerly and easterly parts of the churchyard provide the main visual aspects of the church from the village. The main entrance to the church is along a pathway to the south door and to the east a memorial garden has recently been created providing opportunity for rest and quiet reflection.


Unfortunately for the antiquarian, perhaps, but fortunate for the villagers, St Mary’s church has had rich and generous patrons, in particular the Wilsheres of the Frythe. Consequently in the last 160 years the church has been so remodelled and rebuilt as to obscure every external trace of the original structure. The Wilshere family was well known for its use of Chronograms, Latin inscriptions in which a date is hidden, using letters read as Roman numerals. There are two examples of this interesting eccentricity on the outside walls of St Mary’s.


The present chancel was built in c13, probably on the site of the Saxon chapel. The nave (now 22m×6m) built at the same time, was much altered in c15 and again in c20 when it was extended westward by 6.5m. The south aisle and porch were built in c15 and reinforced in c19 when what is now the St Nicholas Chapel was built over a portion of the graveyard. A memorial in the chapel records the names of those whose graves were covered. The north aisle was added to the nave in c19 and was widened and lengthened in c20. A major c20 rebuild added the vestries on the north side, raised the nave roof pitch to match the chancel and rebuilt the tower. The c19 works, in the Gothic Revival style, were carried out under the direction of the architect Sir Arthur W Blomfield, while the final rebuilding carried out in 1910-11, was designed by his son, Charles J Blomfield.


The present tower, St Mary's third, built in 1910, is a brick structure faced in flint, with a crenellated ashlar top and carved stone gargoyles. There are eight bells hung on an iron frame, seven of them modern and one recast in 1760 and a tower clock, built by John Thwaites of Clerkenwell in 1803, which was refurbished and installed in the rebuilt tower in 1911. The nave roof, together with the chancel, chapel and vestry roofs are covered in plain tiles, with a c15 Sanctus bell above the priest’s vestry. The roofs of the aisles and tower are lead covered. All the walls are faced in flint with stone dressings and, together with the regular stone buttresses, present a unified whole.


Most windows date from c19 with tracery based on both decorated and perpendicular styles. On the west gable of the nave is a c16 window in the perpendicular style, re-installed into the extended nave in 1910, while the east window replaces three Early English lancets which were in a poor state following a fire in the chancel in 1952.


Approaching from the High Street, the church sits foursquare to the street, with the glass doors of the south porch inviting the passer-by to enter across the open churchyard. This is a very successful introduction of simple modern detailing into historic fabric.


On entering the porch, and stepping down into the church, one of the best loved features of the building is displayed, the lightness and brightness of its interior. Most of the interior is in view from the entrance, pointed arcades rise from octagonal columns, those to the north having been rebuilt in about 1910 to match the c15 south arcade. Directly opposite, below an arch of the north arcade, is the font, installed in 1987 in oak and stone, while the former baptistery beneath the tower at the west end of the south aisle has been recently converted to become the parish office.

Through the use of glass doors and walls, sound relayed from the church, the office space is also used as a refuge for parents with restless children who, themselves, can continue to follow the service. The underside of the roofs in the church are plain boarded and stained generally, although the chancel and chapel ceilings are decoratively painted. Floors have stone aisles with woodblock beneath pews.


The nave altar takes a simple form, set beneath the chancel arch on a carpeted platform with removable communion rail. The choir pews have been relocated to the north aisle, adjacent to the organ leaving the chancel space fairly open.


On the north wall of the chancel can be seen the c15 rood screen and nearby part of a c12 arch, while on the south side of the sanctuary is a double piscina from the decorated period. A single piscina of similar date can be seen in the south wall of the south aisle.


The high altar is in oak with fielded panels and riddel frame while the altar of the chapel is ornately carved. The c19 pulpit is of carved oak on a stone base with an oak tester of similar design. The lectern is of oak and freestanding, possibly c20. Pews are of varnished pitch pine, the lightness of which assists the interior. The Rector’s vestry is panelled with stained oak taken from the box pews which were removed in 1870.


There are memorials spanning several centuries in the church, the older incorporated into the 1910-11 rebuilding but, unfortunately, some were lost in a fire in 1952. A floor slab in the chancel marks the place of the re-burial of the Saxon remains found north of the present church. The window glass is mainly c20 with the principal exceptions of the Clayton and Bell windows to the chapel east wall (1869). The ‘Benedicite’ east window, depicting Christ in majesty flanked by the four seasons in pictorial form, is an elegant replacement following the 1952 fire and is highly regarded. The glass was designed by a St Alban’s maker, Christopher Webb.  A recent addition, above the door into Church House, is a window installed in late 2012 commemorating Queen Elizabeth II's Diamond Jubilee and celebrating the London 2012 Olympics.


The tracker-action organ was built by Nicholson’s in 1991 and is considered a very good example in its class. Most of the cost of the instrument was raised in one day by gifts from the congregation and community in memory of Rector Canon Terence Wenham. 


Church House


Church House was completed in 2007, following a major fund-raising initiative  Situated on the north side of the main church, away from the road, it provides wonderful facilities for the chruch and the village. It can be accessed from inside the church, using the doors by the choir stalls, and from the extenal entrance from Church Street on the eastern side of the church yard.


Church House compliments the facilities within the main church, providing space for meetings and Sunday school activities, as well as social events and a weekly community café. The building is also offered for related community uses. Booking is through the church secretary.


Internally, the building is warm and inviting, with views out towards the eastern churchyard and memorial garden.It is  fully disabled-accessible, with a lift by the entrance from the church.

It comprises one main room which divides into three smaller rooms, a fourth ‘quiet’ room, a foyer, a kitchen, toilets and a small, sunny courtyard.


The main room can seat 65 for a sit-down meal and 85 for a lecture, using its integral screen, data projector and sound system. The building is used for the junior church groups and coffee after the main Sunday service.


Church House is designed to high standards, with energy efficiency in mind, and includes ground source heat pumps as part of the integrated heating system.


The number and variety of activities that take place at St Mary’s have increased significantly since Church House opened. Social interaction has increased dramatically which has also led to increased concern and care for each other.


We continue to look for new ways to use this incredible resource.


St Mary’s Bell Tower


There is a long and established tradition of Bell Ringing at St Mary’s and many in the Village comment on the pleasure this sound brings them; maintaining the ambience of Welwyn as a village community with the Church at its very centre for over 1,000 years.


The Church Bells at St Mary’s are rung every Sunday from 9.00am to 9.30am for Morning Service and on the 2nd, 4th and 5th Sunday from 6.00pm to 6.30pm for Evensong. On Tuesday evenings from 7.30pm to 9.15pm, the Bell Ringing Team have their practice. Bells are rung both as a reminder to the Congregation and as an invitation to anyone in the community of Welwyn to come to St Mary’s and join in Christian worship.


In addition, Bells are rung for Weddings when requested.


On certain days of the year the Bells are rung to mark particular Church Festivals and Special Occasions, eg on Christmas Eve at 10.30pm to 11.00pm before Midnight Mass, on Christmas Day and Easter Sunday at 7.30am to 8.00am and at normal Sunday times, on New Year’s Eve and on All Soul's Day. We also ring if a Confirmation or Installation Service is held at St Mary’s and on the morning of the Street Market in Welwyn Festival Week in June.


The Bells are rung to mark or celebrate special State occasions and in 2012 we have been asked to ring in celebration of the Queen’s Diamond Jubilee and the start of the Olympic Games. Occasionally Bell Ringers from other Parishes come and enjoy the ringing of our Bells for an hour or so.


Please see the page on bell ringers.



St Mary's heating system is the result of an exhaustive search by one traditional English church to find the most cost effective way to reduce its 'carbon footprint'. We think it is important that the results being achieved by St Mary's Ground Source Heat Pump (GSHP) system become more widely known and this website is one way of achieving publicity. Each church building offers different opportunities for 'shrinking the carbon footprint' and we think schemes need to be compared in terms of the reduction of carbon dioxide emitted per year and their capital costs.


Our investigations showed that GSHP systems are much better in the UK than Solar Cell installations generating electricity when measured in these terms. For example, on present projections of savings of carbon dioxide emissions, the capital cost of St Mary's system will work out at between £2,000 per saved tonne of carbon dioxide emitted per year. By contrast, Solar Cell systems cost over £7,000 per saved ton of carbon dioxide emitted per year.


St Mary's innovative scheme uses a GSHP system running on purchased 'green' electricity to heat both a Grade II Listed Church and a new Church House constructed with high standards of insulation. The system is dimensioned carefully to make the maximum use of GSHP heating, only reverting to carbon based gas heating in the coldest weather. The system has a very high level of instrumentation and data logging so that performance can be accurately measured and compared to predicted results.


If you're new to the idea of Ground Source Heat Pumps try the FAQ section, then dip into the Brochure.


Brochure produced before the system was installed in 2007


System Overview


Our two buildings are of fundamentally different construction and our challenge was to provide an environmentally friendly heat source that could heat both buildings.


The Church is a grade II listed building with Edwardian cast iron radiators and was originally designed to be heated by water circulating from a coke fired boiler.  Up until recently the Church had been heated by a gas boiler which replaced the coke boiler, and operated with water temperatures up to 80°C.


Church House is a modern building built with very high standards of insulation and employs under-floor heating and the circulating water enters the system at a temperature of 30° - 40°C.


Our Objective was to minimise the amount of Carbon Dioxide we released to the atmosphere.  A comprehensive evaluation of possible environmentally friendly heat sources took place between 2003 and 2005, from which it became clear that the only viable solution, bearing in mind the that the Church is in the centre of a conservation area, was to use Ground Source Heat Pumps.


Heat Pumps are most efficient when providing water flows at around 30°C such as that used with under-floor heating, when the heat pump coefficient of performance (COP) - the ratio of energy output to energy input - can achieve a figure as high as 5.  Unfortunately the efficiency drops considerably as the output water temperature rises.  Experiments with the Church heating were carried out over two winters, using the gas boiler, from which it was established that a water flow temperature of 55°C could maintain the Church at an ambient temperature of between 16 and 18°C provided the outside temperature stayed above about 4°C.  From heat pump performance data it was established that under these conditions a COP of 3 should theoretically be achievable making assumptions about borehole temperatures.


The Experiments also showed that this continuous heating regime made the Church much more welcoming, more comfortable and reduced our maintenance costs for an approximate 20% increase in energy cost, when compared with only providing heat for when the Church was occupied.


We achieve in practice a Seasonal Performance Factor,  which is the ratio of energy output to energy input over a heating season of the heat pumps, of around 2.5 - not 3.0.  The reasons for the departure from the theoretical figure are that the boreholes run a little colder than we anticipated and there are more losses in the system than we had anticipated.  With energy costs at current levels, we calculate that, using the mixture of heat pumps and gas that we do, the system running costs are about the same as if we just used gas heating.  We use as much off-peak GSHP heat as possible and rely on the mass of the stone Church to act as a heat store.  The gas boiler is used primarily for top-up heat during peak rate electricity periods and also if the outside temperature falls below around 4°C, when we need to raise the water flow temperature above 55°C to obtain sufficient heat for the Church.  As gas prices are expected to rise faster than electricity in the future, we expect to make future savings.


We Use three heat pumps and a gas boiler in parallel and we can select 1, 2 or 3 heat pumps or switch entirely to gas if the situation warrants it.  Church House is fed with water from the Church system regulated by a special valve so that the under-floor heating can be run at between 30° and 40°C.


Each Heat Pump is connected to an array of six boreholes in the churchyard, making eighteen boreholes in total.  Most GSHP systems feed a brine/water solution through plastic pipes into the boreholes to extract heat.  For St Mary's, using this system, we were told, would require 10 boreholes 100 metres deep.  On enquiry we found that the capital cost for 10, 100m bores was prohibitive and we have, instead, used an alternative method, pioneered in the USA, that feeds the Heat Pump refrigerant through copper piping in the boreholes.  This is a more efficient solution allowing the same amount of heat extraction using 18 boreholes drilled to a depth of only 30 metres.  The capital cost savings of this method were fundamental to the project going ahead.


This approach, together with our use of green electricity, minimises our Carbon Footprint whilst maintaining a realistic economic balance.




What's it all about?

St Mary's Church, Welwyn has recently built an extension to the church building to provide meeting rooms and facilities for the congregation and the community.  The new building, Church House, and the church itself are heated by Ground Source Heat Pumps.


To reduce the amount of Carbon Dioxide released into the air and save on heating bills in the long term.


Because Carbon Dioxide is a Greenhouse Gas and is causing Climate Change.

How Much Carbon Dioxide?

It is estimated we shall avoid releasing around 25 tonnes of Carbon Dioxide a year.

What's a Ground Source Heat Pump?

Heat pumps are more normally used for industrial cold stores. In our case three electrically driven heat pumps are connected to a system of pipes drilled into the churchyard. From them they collect ground heat which is compressed to a higher temperature and used to heat the church buildings. For every unit of electricity used by the heat pump, we get around three units of heat.

Why doesn't every one use one?

In many countries lots of people do. There are hundreds of thousands of them throughout USA and Europe. They are more expensive than a gas boiler and drilling the boreholes is an extra cost.

How Much Did It Cost?

The system cost us around £50,000.

Is the installation working as planned?

Yes! Initial results are in line with the performance predictions made from theoretical studies and from measurements of the earlier church heating system over the two previous winters

More Information?

You can contact us by email.

The Church History
Church House
St Mary's Bell Tower
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