Table 1
The four principles (4 C’s) and subprinciples for moisture management in the British Standard Institution’s (BSI) White Paper.
| PRINCIPLE | SUBPRINCIPLE |
|---|---|
| 1. Compatibility with the context | Geography |
| Built form | |
| Materials and construction method | |
| Condition | |
| Use | |
| 2. Coherence | Coherence of moisture approach |
| Thermal coherence | |
| Airtightness | |
| Weathering/waterproofing | |
| Ventilation, heating and insulation | |
| 3. Capacity | Design |
| Process | |
| 4. Caution | Usability |
| Maintenance | |
| Monitoring | |
| Feedback |
[i] Source: May & Sanders (2017).
Figure 1
First draft (left) and final version (right) of the devised risk-management process.
Table 2
Energy and moisture risk-management framework.
| STAGE | ASSESSMENT/PLANNING | TECHNICAL DESIGN/SPECIFICATION | CONSTRUCTION/INSTALLATION | HANDOVER/USE |
|---|---|---|---|---|
| Core tasks during the stage | Assess the Context of the building(s) and devise a compatible overall approach that also meets all other design objectives | Apply a strategy for detailed design following principles of Coherence | Undertake moisture-safe construction according to the specification and principles of Coherence, Capacity and Caution | Handover documentation and operational guidance to users Implement any required measures of Caution |
| Conditions to be assessed or considered during the stage (specific to each retrofit measure) | See Table 3 as an example (solid-wall insulation) | See Table 4 as an example (solid-wall insulation) | See Table 5 as an example (solid-wall insulation) | |
| Documentation for information exchange (at the end of the stage) | Document the assessment and planning in a formal strategy List a set of suitable retrofit measures | Produce a detailed specification and instruction document with requirements for quality control | Document the actual construction process and all amendments and alterations from the specification | Document the additional interventions occurring after the retrofit (including maintenance) Store the monitoring and evaluation results |
Table 3
Pre-retrofit conditions to be assessed based on the principle of context to evaluate the existing risks for a solid wall.
| ASSESSMENT | CONSEQUENCES | |||
|---|---|---|---|---|
| MODE | METHOD | MOISTURE | ENERGY | |
| Geography and climate | ||||
| Assess prevalent wind direction | Desktop | Air infiltration | ||
| Assess wind-driven rain exposure | Desktop | BS 8104 (BSI 1992) | Rainwater penetration | Increased heat transfer |
| Assess the ability of the existing construction to resist driving rain | Rainwater penetration | Increased heat transfer | ||
| Conditions | ||||
| Assess the condition of vulnerable elements (e.g. rot or fungal attack for timber joists, corrosion for metal), especially if structural | Visual inspection; measurement | Moisture meters (e.g. microwave; moisture pins) | Structural damage | |
| Assess the condition of the external finish (e.g. render, pointing, mortar continuity, paints or coating) to check for cracks and damage, and assess if a repair is needed | Visual inspection; measurement | Thermography | Rainwater penetration | Localised increased heat transfer |
| Assess the quality and suitability of rainwater management (e.g. sill/verge overhangs, roof eaves, rainwater goods, drainage), and assess if a repair is needed | Visual inspection | Rainwater penetration | Localised increased heat transfer | |
| Assess the quality of seals around doors/windows | Visual inspection | Smoke pen | Water infiltration | Air infiltration; thermal comfort |
| Assess the whole-building air tightness | Measurement | Blower door test | Indoor moisture excess | Air infiltration; thermal comfort |
| Assess the existing moisture problems if any (e.g. mould, damp, condensation) on and within walls, junctions and adjacent elements (e.g. ceiling, floor), and investigate the cause(s) of the problem for possible repairs | Visual inspection; measurement | Thermography; moisture meters (e.g. microwave) | Occupants’ health; damp; structural damage | Increased heat transfer |
| Assess the whole-building thermal performance | Desktop; measurement | Annual energy usage (e.g. bills, smart meters); heat transfer coefficient (HTC) evaluation (e.g. co-heating) | Heating/cooling loads | |
| Assess the indoor environmental quality (IEQ) | Measurement | IEQ sensors (e.g. temperature and relative humidity) | Indoor moisture excess; mould growth | Thermal comfort; heating/cooling loads |
| Built form | ||||
| Assess the complexity of the built form and details to evaluate the ease and suitability of retrofit interventions | Desktop | Architectural drawings | Rainwater penetration | Potential thermal bridging |
| Materials and construction method | ||||
| Identify the existing construction method | Desktop; visual inspection | |||
| Identify the existing materials and their properties | Desktop; visual inspection; measurement | Tests: U-value; thermal conductivity; water absorption | Excess moisture | Heating/cooling loads; energy balance |
| Identify the existing rainwater protection | Visual inspection; measurement | Water absorption test | Rainwater penetration | |
| Use | ||||
| Assess the existing ventilation system and building services (e.g. heating) and whether they need upgrading | Visual inspection; measurement | Opening areas; air flow measurement in ductwork | Indoor moisture excess | Air infiltration; heating/cooling loads |
Table 4
Conditions to be considered based on the principle of coherence to evaluate the risks of retrofit strategies for solid walls.
| ASSESSMENT | CONSEQUENCES | |||
|---|---|---|---|---|
| MODE | METHOD | MOISTURE | ENERGY | |
| Coherence of the moisture and thermal approach | ||||
| Assess building performance with the retrofit measure(s) proposed | Desktop | Dynamic building performance simulations | Indoor moisture excess | Energy balance; heating/cooling loads; thermal comfort |
| Assess the extent of moisture interactions in the build up of existing walls (e.g. the presence and type of render, plaster) | Desktop; visual inspection | Hygrothermal simulations, according to EN 15026 (CEN 2007) | Excess moisture; interstitial condensation | |
| Assess the moisture risk with the retrofit measure(s) proposed to understand the influence of factors such as climate, exposure and orientation | Desktop | Hygrothermal simulations | Excess moisture; mould growth; occupants’ health | (Localised) increased heat transfer |
| Identify any standard and non-standard obstacles (e.g. fences, walls, satellite dishes, hanging baskets) that will require specific detailing to overcome thermal bridging | Desktop; visual inspection | Architectural drawings | Condensation; mould growth | Thermal bridging |
| Airtightness | ||||
| Identify any standard and non-standard obstacles that will require specific detailing to overcome air leakage | Desktop; visual inspection | Water vapour infiltration; interstitial condensation | Air infiltration; thermal comfort | |
| Assess the impact of the retrofit measure(s) on seals around doors/windows and identify if specific detailing will be required to overcome an air leakage | Desktop | Water vapour infiltration; interstitial condensation | Air infiltration; thermal comfort | |
| Assess the compatibility of the retrofit measure(s) on the whole-building air tightness (compared with pre-retrofit conditions) | Desktop | Indoor moisture excess | ||
| Weathering/waterproofing | ||||
| Identify any standard and non-standard obstacles that will require specific detailing to overcome moisture ingress (e.g. rainwater penetration) | Desktop; visual inspection | Rainwater penetration | Increased heat transfer | |
| Ventilation/building services | ||||
| Assess the compatibility of the retrofit measure(s) with existing services (e.g. services in the way) | Desktop; visual inspection | Excess moisture; mould growth | Energy balance; heating/cooling loads | |
| Assess the compatibility of the existing ventilation system with the retrofit measure(s) and whether it needs upgrading | Measurement | Opening areas; air flow measurement in ductwork | Indoor moisture excess; occupants’ health | |
Table 5
Conditions to be assessed based on the principle of caution to evaluate the long-term risks of the retrofit strategy for solid walls.
| ASSESSMENT | CONSEQUENCE | |||
|---|---|---|---|---|
| MODE | METHOD | MOISTURE | ENERGY | |
| Usability | ||||
| Provide adequate handover (e.g. documentation on fixings for insulated walls, ventilation) | ||||
| Maintenance | ||||
| Plan maintenance of the external facade (e.g. render, pointing) | Rainwater penetration | Thermal bridges; increased heat transfer | ||
| Keep rainwater goods and drainage in good condition | Rainwater penetration | Localised increased heat transfer | ||
| Monitoring and evaluation | ||||
| Monitor the overall energy use in the building | Measurement | Utility meters | Heating/cooling loads | |
| Monitor the energy use of the individual systems | Measurement | Submeters | Heating/cooling loads | |
| Perform a Post-Occupancy Evaluation (POE) | Survey; interviews with the building’s users | Mould growth | Thermal comfort | |
| Monitor the indoor environmental quality (IEQ) (e.g. temperature, relative humidity, CO2) | Long-term measurement | IEQ sensors | Mould growth; occupants’ health | Thermal comfort; heating/cooling loads; occupants’ health |
| Measure heat losses through the insulated walls | Measurement | U-value test | Heating/cooling loads | |
| Measure heat loss through the whole building envelope | Measurement | Heat transfer coefficient (HTC) evaluation (e.g. co-heating) | Heating/cooling loads | |
| Assess the airtightness of the building envelope | Measurement | Blower door test | Water vapour infiltration | Air infiltration; thermal comfort |
| Assess the moisture content of the insulated wall | Measurement | Moisture meters (e.g. microwave) | Excess moisture; mould growth; structural damage | Increased heat transfer |
| Perform a condition survey of insulated walls and junctions | Visual inspection; measurement | Thermography | Mould growth | Thermal bridges |
| Monitor the conditions of vulnerable elements (e.g. joist ends, wall–insulation interface) | Long-term measurement | Embedded sensors (e.g. temperature, relative humidity, moisture content) | Mould growth; interstitial condensation; structural damage | |
| Feedback | ||||
| Periodically review the performance of the retrofit project and update the risk management based on the emerging knowledge | ||||