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Laws of Unitended Consequences

The law of unintended consequences is alive and thriving in the Retrofit sector!!

Unintended consequences arising from poorly designed or executed EWI, IWI and CWI retrofit projects are well documented (BRE & ESRI). Many have either health or economic consequences arising from these disjointed delivery processes.

Energy Usage
Recent research in the UK suggests that current retrofit measures may not be as effective as anticipated. A range of issues from poor workmanship to incorrect assumptions regarding existing construction and the impact of the “rebound effect” in occupants. Similarly, in research conducted on EWI installations by TU Dublin, it was shown that while overall comfort levels increased, not all cases showed a reduction in heating fuel use or any improvement in energy efficiency behaviour. Fuel consumption was shown, in many cases, to remain the same or even increase as users choose, for example to heat the entire house as opposed to a portion of it. Occupants were also likely to use the same amount of energy to achieve more comfortable conditions overall, known as “comfort take-back”. Comfort take-back is a major cause of the rebound effect, a phenomenon whereby households consume more energy than predicted after energy efficiency upgrade. In general, the main motivation for retrofit was found to be comfort and not energy savings or environmental concerns.

The typical person spends 90% of their time indoors, with 65% spent in their home. In May 2023, the US based Centers for Disease Control and Prevention recommended five so-called air changes per hour — the equivalent of replacing all the air in a room — in all buildings, including schools.
Research by the ESRI highlighted how increased air tightness and levels of insulation, arising from retrofitting measures can lead to higher levels of mould growth. This is attributable to a lack of adequate ventilation or incorrectly installed insulation which allows condensation to occur. For instance the application of IWI can mean that the external wall is no longer dried by heating from the interior of the dwelling, which can in turn cause long term structural damage.

Current methods of assessing durability and condensation risk are undertaken using unrealistic parameters for risk such as levels of high exposure to wind driven rain and high levels of internal and external relative humidity. These limited methods of testing can provide a level of comfort and assurance which in reality may not be delivered in practice. Condensation calculations do not properly account for weather in many of our Regions. In addition, any increase in relative humidity may negatively impact on un-treated thermal bridges within dwellings.

Indoor radon concentration levels are also affected by the air exchange of a building. As such, buildings which are better ventilated have lower levels of indoor radon concentration. Given that Ireland has relatively high levels of indoor radon it is important to ensure that retrofitting measures which increase the air tightness of a building, do not also increase indoor radon levels above the national reference level.

Cavity Wall Insulation
In cavity wall construction, the cavity will almost certainly be ventilated as this is how it does its job as a cavity. However this means that heat from the house penetrating the internal skin to the cavity will be exhausted into the atmosphere by that ventilation. This feature then compromises the performance of any EWI system.

Testing of Insulation Materials
The majority of materials testing takes place in a steady state condition and may not be reflective of the dynamic conditions associated with our weather and the many different construction methodologies. Testing therefore may not reflect the As Built In Service (ABIS) conditions of buildings. This disconnect between the performance of materials in test and in use may be the cause of the “performance gap” experienced by many homeowners.