Proposed works

Reason for works

The dwelling was sold to the current owners at a point where rot, dampness, substandard drainage, a substandard extension, shifting roof tiles and failing flashings had conspired to make the dwelling uninhabitable. Significant repair and maintenance works are necessary. There is no insulation, all services need to be replaced. Fire compartmentation must be completed.

Design

The dwelling was purchased in very poor condition. Nonetheless, some fittings and a large amount of building fabric have survived. The proposed renovation is a balance between preservation, habitability, comfort and building regulations compliance. Mass concrete walls and internal joinery will be saved, as will externally cast-iron gullies, boot scraper, cast-iron grilles, chimney stack and roof tiles. Given specific conditions, it is proposed that the original lathe-and-plaster ceilings be removed. Replica hall door and chinoiserie windows will be installed to recapture some of the original design and quality.

The creation of the ‘major renovation’ standard has implications for what measures a homeowner of an existing dwelling (which is not listed on register of protected structures) may consider. In brief, renovating more than 25% of the surface area of an existing dwelling (where that includes some form of wall insulation) triggers the requirement for a cost-optimal improvement which is identified as 125 kWh/m2. See Section 2.3.1 and 2.3.2 of TGD-L:2018. Section 2.3.1 states “Where more than 25% of the surface area of the dwelling envelope undergoes renovation the energy performance of the whole building should be improved to Cost Optimal level in so far as this is technically, functionally and economically feasible.”

Given the almost ruinous state of the dwelling, the extent of works constitute a ‘major renovation’ under the revised Part L (2018) of the building regulations.  For this reason, presenting a minor renovation was not considered.

Given the thermal performance that will be achieved, there is an opportunity to install a single integrated, electrically-powered, mechanical system that provides ventilation, space heating and hot water. Having only one energy services company brings a reduction in standing charges, while one system reduces complexity and services-related maintenance regime. Delivering heat through ventilation removes the necessity for fireplaces and radiators in a small house. The approach will contribute to the national drive to decarbonise Ireland’s energy systems. Heritage value can be maintained in the process of works proposed.

Proposed maintenance & energy-efficiency focused works

Description of proposed major renovation upgrade project and heritage impact

Lathe and plaster

It is hard to save sloped ceilings because they are difficult to insulate without loss of the sloped plaster and lathe ceilings.

Gutters & downpipes

Gutters and downpipes are often one of the least maintained parts of a property. As they play a vital role in taking water off the building, it is advisable to have them checked at the start of every autumn (before leaf fall). Gutters filled with leaf mulch and eventually weeds lead to a greatly increased risk of water spilling down the elevation, or worse leaking into the building. Due to a lack of maintenance many original cast-iron gutters and downpipes rust or lose brackets and become detached. Sadly, many homeowners remove these, often replacing them with uPVC due to lack of awareness that they can be repaired and parts replaced, and that several Irish companies specialise in this. Replacement rainwater goods in inferior materials detract from the architectural character, provide unsatisfactory connections to surviving sections and in general perform less well in terms of durability, repair, etc. Even modest features such as original grilles and gutters can have heritage value.

Internal wall insulation

Arguably, wall insulation is less important in this dwelling than floor or roof. Insulating walls in such small dwellings is problematic in any case. Externally insulating the front elevation would require Planning Permission because the footpath onto which the entrance door opens is in the public domain. The owners have stated that they don’t want to install internal wall insulation as it would reduce internal floor area. For this reason it has been excluded.

The early concrete is almost akin to a rubble wall in characteristics. At the same time, the painted render finish has very low water absorption, reducing hygrothermal risks for internal wall insulation.  Formal risk assessment should be undertaken.

Despite small rooms sizes, owners may be willing consider 25-40mm of fully bonded insulation. This will increase comfort, warm surfaces and reduce risk of surface condensation.

Measuring Radon

Radon is a natural gas that is usually found in igneous rock and soil. Leakage of radon into buildings is the greatest health risk from radiation in Ireland and accounts for more than half of the total radiation dose received by the Irish population. The government has set an annual average radon concentration of 200 becquerels per cubic metre (Bq/m3) as the action level above which remedial action to reduce indoor radon levels should be considered.

Technical Guidance Document C (available free from http://www.housing.gov.ie) contains a map of gridded cells coloured to indicate the various concentrations of radon measured in a national survey. Dublin City and suburbs are covered by four of these cells, three of which indicate that less than 1% of the dwellings measured had radon radiation levels above 200 Bq/m3. The cell for Southeast Dublin indicates 1-5% of dwellings registered this level of radon. It is nonetheless possible that a district within a cell categorised as low risk might be higher risk due to local geological conditions, so all householders are advised to measure. The Environmental Protection Agency (www.epa.ie) has a list of approved radon meter suppliers. For a small charge, the applicant is posted two palm-sized monitors to locate in the property for a month. After returning the monitors, a report is posted to the homeowner listing the levels found.

Because the proposed works to the floor exclude the installation a radon barrier, it was judged necessary to measure the radon levels present. The average radon concentration was measured at 39 (Bq/m3). Despite the level being so low, the radon testing company advised that the levels get re-tested after all works are done.

Vapour permeable insulated solid floor

It is proposed to install a breathable floor system particularly suited to solid wall structures. The insulant and the aggregate usually used under the radon barrier are combined in this case in the form of a foamed glass aggregate insulation. Based on DADC drawings, it appears the dimension from floor finish to top of sub-slab (i.e., the floor of the underfloor void) in these dwellings is generally about 500mm; in the case study dwelling, it is more than 700mm. The ‘sub-slab’ is a concrete ‘crust’ no more than an inch thick laid directly on boulder clay.

The proposed solid floor buildup is install (LABC-approved) foamed glass aggregate with limecrete slab in existing floor void. 0.12 U-value.

This level of caution is necessary. As a further caution, it is suggested that a ventilation system featuring constant extraction be installed and commissioned. This could be a mechanical extract ventilation (MEV) or mechanical ventilation with heat recovery system (MVHR).