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    Review of 'Moisture control design has to respond to all relevant hygrothermal loads'

    Moisture control design has to respond to all relevant hygrothermal loadsCrossref
    A must-read overview on the development of hygrothermal simulations and standardisation.
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    Moisture control design has to respond to all relevant hygrothermal loads

    Moisture related damage is still a formidable cost factor in the building sector. Besides installation deficiencies, moisture control design failures are the most frequent reasons for moisture problems. Therefore, adequate moisture control analysis has become the key for sustainable buildings. However, by focusing on vapour diffusion only other important moisture loads such as driving rain, construction moisture or air infiltration are mostly neglected. Therefore, international moisture control standards often refer to simulation models for more realistic analysis, leaving many practitioners wondering how to handle these tools. To overcome this dilemma, the updated German moisture control standard has introduced a three-pathway approach for design evaluation: 1 st deemed to satisfy list, 2 nd restricted Glaser calculation and 3 rd fully fledged hygrothermal simulation. The third pathway includes the option to account for small leaks or imperfections in building envelope components. Guidelines in other countries are also embracing similar moisture control approaches which gives hope for more durable and sustainable building design. To reach this aim, moisture control should also become an integral part of the design process instead of a secondary chore.

      Review information

      This work has been published open access under Creative Commons Attribution License CC BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Conditions, terms of use and publishing policy can be found at www.scienceopen.com.

      Built environment,Sustainable development,Moisture control design standard; hygrothermal simulation; vapour diffusion calculation; deemed to satisfy; component leaks;

      Review text

      This article presents a timely overview on the development of hygrothermal simulations and protocols for the consideration of appropriate moisture mechanisms and sources. It presents some of the challenges associated with the most common assessment method, the "Glaser" method, and justifies the need for an approach that assesses moisture risk under as-built, in service conditions. It also presents some useful examples of international and national standardisation, showing how the building physics community worldwide is advancing towards a more appropriate assessment method, and presenting some of the challenges. This is a must-read article for everyone who is using hygrothermal simulations in their practice or research work.

      Please find below some comments and points that need clarification.

      In section 1, can you please be more specific regarding "renewable insulation materials"? Are you referring to natural (or bio-based) materials ?

      Typos in 2.2: "lessoer requirement"; "most cladding systems are generally directly fixed"; "are also very common, only few damage cases had been reported". Section 2.2 would be better renamed as "Wind-driven rain" - the section on solar vapour drive is in 2.3.

      In 2.3, the statement "the cavity of masonry walls should net be ventilated", could be rephrased to "Considering all aspects, it is preferred for the cavity ...". Also, in some areas (e.g., high wind-driven rain exposure) a slight ventilation might still be important; in these areas, it is also likely that cavity wall insulation cannot be installed. Can you comment on this?

      Section 2.3 does not mention solar vapour drive in solid masonry walls. Can you please expand on this? There is evidence that solar vapour drive occurs in solid masonry walls, and - if appropriate insulation is installed - moisture can reach the indoor environment and leave the building (via appropriate ventilation) without accumulating in the wall or indoors.

      In section 2.4, you could mention the different heating methods in buildings such as churches (e.g. IR heating?), which lead to a non-uniform indoor temperature.

      In section 2.5, CSB is Calcium silicate Brick. What do you mean with "green" wood? Also, it would be good to know in which country the fire safety regulations require window head insulation to be mineral wool. Is it Germany? Australia?

      In section 2.6, why is moisture from the ground a problem only for structures with crawl spaces? Can you please elaborate on this or add a reference? The last word of the paragraph could be "options" rather than "settings".

      Section 3 could be renamed "considering construction imperfections in the evaluation of moisture risk", as the chapter is not on moisture sources, but on how they are considered in simulations.

      In section 3.1, is the drainage at window connections the only provision for a successful EWIS? In the UK, the failure of a EWI project highlighted other areas such as the eaves detail (see https://passivehouseplus.ie/news/health/disastrous-preston-retrofit-scheme-remains-unresolved).

      In section 3.2 (towards the end), please change "juristic" to "legal". It is unclear where the legal implications are: are you referring to the choice of air permeance in the design? Or in the model, for diagnostics of failure? Can you explain this in a bit more detail?

      In section 4, do you have any references on failures with lightweight blocks?

      In 4.1, I haven't heard of "mineral foam insulation"; can you rephrase to " mineral insulation boards" or "mineral-based insulation panels", and provide an example (e.g. Calcium-silicate)? Also, what do you mean with "respectively in the calculation tool"? Can you please rephrase this sentence?

      In 4.3, can you provide some examples on the restrictions that have to be observed?

      In 4.4, it is great to see that BS 5250 is in line with other national standards. The recent update of BS 5250 includes the requirement of hygrothermal simulations according to EN 15026 for traditional solid masonry walls located in areas of high exposure to wind-driven rain.





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