We were freezing!” says Caitríona Fisher of Co Dublin. “When I saw frost on the inside of the bay window in the sitting room, I knew I had to do something. It was terribly cold. Also it doesn’t help that this particular room is north facing and shaded by vegetation!”
“These Victorian houses just weren’t built for the kind of cold we’ve been getting in recent years,” she adds. The house has been renovated in the past and currently has radiators throughout which are fuelled by a gas boiler.
“Because it was a Victorian house, we asked the Georgian Society to recommend someone with experience to guide us through the renovations. We needed a well thought out plan.”
As the building isn’t listed they didn’t require planning permission to carry out internal works but wanted expert advice to guide them through preserving the building’s integrity while carrying out an energy upgrade.
The living and dining rooms are built as is typical for the time with suspended timber floors, both of which have a three foot deep void underneath. “You could feel the cold between the gaps of the old boards. The wind actually came up through them!”
The kitchen, which is at ground level and accessed via a series of up/down steps, needed attention too. “The floor there was also cold but for different reasons. Tiles had been laid in a previous restoration straight onto the original terracotta floor, which was the only thing separating the house from the ground below,” she explains.
“We had to take it all up and at this stage we considered underfloor heating; the estimate came to €9,000 and just decided to do it. It’s the best thing I ever did! It’s a different, much gentler heat, simply amazing. It’s just a pity I couldn’t do it on the rest of the house.”
Another thermal element that required attention was the front bedroom floor, which was partly over the porch so they insulated the porch ceiling to plug the leak.
The main reason for that bedroom being cold was its north facing orientation and window. “The very small ensuite and a walk-in wardrobe in the northeast corner were freezing cold with mould against the wall,” shivers Caitríona.
“The solution was to insulate the walls from the inside and it really is a much warmer space now.” The old lime walls require breathable materials so the wall was lined with a 50mm calcium silicate board which was lime plastered over.
The best piece of advice Caitríona says she can give is to take daily photographs of the work that’s been completed. “My daughter took pictures every evening of wherever the builders worked; afterwards when there were problems we were able to go back through them and see why.”
“Even simple things like where a stud was positioned is good to know – reality doesn’t always exactly match up to design drawings!”
They’ve come across two issues since the works were completed; one is that the kitchen party wall is damp – the wrong type of plaster was put on it – and the other more immediately worrying is in the sitting room.
“Last July, a year after the floor insulation work on the floor had been completed, we found a mushroom,” she confides. “There had been dry rot in the bay window from a blocked rain pipe which was treated during the insulation work but had now re-surfaced in a different areas.”
Out of the gutter
Mould growth is due to damp or humid conditions so the architect and builder set out to find the root cause; they were convinced it was due to a crack in a gulley. “This however didn’t really explain why the humidity was so high – data loggers that were later put in the underfloor void showed 90% to 95% levels. As there are walls supporting the floors which had no gaps for cross-flow of air we started talking about boring holes for ventilation, to allow air to pass freely in the subfloor from the front to the back of the house.”
As discussions were ongoing, another type of mould appeared. “It spread right across the floor! We were told the speed at which it invaded the wood indicated that it was cellar rot.”
Caitríona eventually decided to hire a drain surveyor for €400 in an effort to identify the source of the high moisture levels in the subfloor walls. The source of the problem was a front gully. “It turned out the original gully cement seal around the front footpath had completely gone, something we’d all missed!”
“It was impossible to see as this particular drainpipe goes into another and what happened was the pipe slipped out by the wall, which is why we didn’t notice, and water dripped onto the old exit of the drainpipe, near the base of the wall.”
“That’s all it took for water to seep into the rising walls. We’ve decided to go ahead and bore the holes in the subfloor walls; we’ll then be leaving it to dry out.” The rot has been treated and the insulation removed; once humidity levels drop they plan to put the insulation back in again.
The situation is actually a common one; rainwater goods cause the most harm to buildings, which is why an annual maintenance regime, while onerous is essential.
But as Caitríona points out it’s easier said than done. “You need binoculars to see what’s happening on the roof! In our case, things were let go but in fairness some were so hard to see.”
“But despite the headache you do need to spend the time once a year to have a look at the gutters and at the minimum clear them out,” she adds.
Caitríona says their conservation architect managed their expectations from the beginning. “He warned us an energy upgrade would not make the house excessively warm but just more liveable, and he was right.”
“We didn’t save on our energy bills, as we heat it more, but it is so much more comfortable.” The attic insulation was upgraded from an existing 100mm mineral wool to 300mm. The internal walls were insulated in the return where there were no cornice/wall features with 50mm calcium silicate board. Again the reason for its use is hygroscopic; it’s vapour permeable and capillary, allowing the wall to dry out as they were intended to deal with the humidity caused by driving rain.
The warm walls required a window upgrade as there was a concern that an increase in the heat retained by the walls would lead to condensation on the single glazing; also less than 40% of the sash windows had retained historic glass. They were able to keep the original Victorian sashes; while they had deep frames standard double glazing unfortunately couldn’t be used due to weight so they chose a slim line version with krypton gas, instead of the usual argon.
The house is now a C3 on the BER scale (theoretically at least, as the under floor insulation needs to be reinstated), which indicates roughly the same energy loss as what you could expect in a typical Irish house.
“I’m still reeling from the rot experience. If I won the lotto I’d build a passive house!” But would she miss the centuries-old charm? Chances are, she just might… ν
House size: 180 sqm
Site size: 350 sqm
Year of construction: 1890
BER: From an E1 to a C3
Construction type: brick walls, two storey semi-d, finish red brick laid in Flemish bond[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]List of retrofit measures with costs