Part of the BRE Trust

BRE: The breathed environment indoorsColin KingDate 12th April 2017

Retrofit to older properties

– Important to understand the difference in how buildings perform

– Vapour open and vapour closed

Naturalventilation

Naturalventilation

Pre-retrofit house

Adiabatic zoneMid-terraced: assume negligible heat loss

Wind-driven heat loss Significant ventilation heat loss via infiltration, e.g. around original windows

External walls Uninsulated – high rate of heat loss

Pre-retrofit – moisture generation

Moisture generation per day4 people, 8 hours awake; 8hours asleep ≈ 3 kgcooking (gas hob) ≈ 2-3 kg

washing up ≈ 0.3 kg

bathing ≈ 0.8 kg

clothes washing and drying≈ 1.5 kg

Total average 8.5 kg per day ranging from 3.5 kg for 1 person to 14 kg for 4 people

Values from BS5925

What happened to the ventilation?

Naturalventilation

BS5925:Code of practice for ventilation principles and designing for natural ventilation, recommends (for sedentary occupants):– 16 l/s/person - Some smoking– 24 l/s/person - Heavy smoking– 32 l/s/person - Very heavy smoking

Rate should also relate to ventilated volumeDomestic ventilation systems do not have the required capacity(between 4 and

5 x ADF rates).Should they?

Analysis of the Scale 1500 properties

Insufficientordefectiveinsulation

35%

Ventilationrates33%

Sealingjointsandinternalleaks

10%

Defectivedampcourses,trappedmoisture

22%

SoucesofMouldGrowthinDwellings

Insufficientordefectiveinsulation Ventilationrates Sealingjointsandinternalleaks Defectivedampcourses,trappedmoisture

Unintended Consequences

– No ventilation strategy in place– Building Regulations not helpful (make

it no worse)– Moisture creation internally becomes

excessive due to lack of natural or adequate mechanical ventilation

Unintended Consequences