Airex Floorvent Compliance with Building Regulations and Government Guidance
In this guide, we review the key sections of Building Regulations Approved Document C and the Guide to Best Practice for Retrofit Floor Insulation - Suspended Timber Floors. Specifically focusing on underfloor air space ventilation, we showcase how our innovative Airex Floorvent not only complies with the outlined regulations but also supports best practices in achieving optimal underfloor ventilation. From meeting the dimensional requirements to enhancing cross-flow and monitoring capabilities, Airex Floorvent stands as a reliable solution for creating a healthier and more efficient living environment.
Building Regulations Approved Document C
The relevant section for ventilation of suspended timber floors is 4.14 b).
Ventilated air space measuring at least 75mm from the ground covering to the underside of any wall plates and at least 150mm to the underside of the suspended timber floor (or insulation if provided).
As Airex Floorvent is installed into the outer walls of the building, the dimensions of the underfloor space are unaffected, in contrast to some underfloor insulation methods. If, as is sometimes the case in retrofit, the dimensions are not compliant, Airex Floorvent does not make the situation worse.
Two opposing external walls should have ventilation openings placed so that the ventilating air will have a free path between opposite sides and to all parts.
In retrofit projects, this should be achieved where possible. Where this is not possible Airex’s monitoring capabilities can be used to identify properties at risk and that may need further remedial work to address lack of cross-flow ventilation. Note that in many properties with suspended timber floors air infiltrates from the floor void into the home. In the absence of other underfloor insulation, Airex Floorvent installation does not affect this, potentially providing an additional ventilation path that may ameliorate the lack of crossflow.
The openings should be not less than either 1500mm2/m run of an external wall or 500mm2/m2 of floor area, whichever gives the greater opening area. Any pipes needed to carry ventilating air should have a diameter of at least 100mm.
The certified ventilation area of each Airex Floorvent brick is 4315 mm2. Note that this is significantly more than most conventional air bricks, so if existing ventilation is compliant, replacing existing air bricks with Airex Floorvent will be compliant too. Nevertheless, appropriate calculations should be carried out to ensure compliance where it is possible to achieve it.
Ventilation openings should incorporate suitable grilles that prevent the entry of vermin to the sub-floor but do not resist the air flow unduly.
Airex Floorvent incorporates a grille that is compliant with this requirement ensuring free and efficient flow of air when the vents are open. This requirement does not imply that vents should be open at all times. Airex monitors the underfloor environment to ensure that ventilation is adequate and effective in managing humidity and protecting the timber floors.
If floor levels need to be nearer to the ground to provide level access sub-floor ventilation can be provided through offset (periscope) ventilators.
Airex Floorvent can be fitted into the outer port of periscope ventilators if these are required and this will provide the same heat loss reduction and ventilation as if replacing conventional air bricks.
Guide to Best practice - Retrofit Floor Insulation - Suspended Timber Floors
While this document does not have regulatory force it is helpful guidance in best practice for retrofit projects to ensure good outcomes. The key sections on ventilation of the dwelling and underfloor air space are cited below.
Ventilation to the main dwelling
52. The ventilation provision to the main dwelling should be assessed to ensure that the building will not become less compliant than before the measure was considered for installation. This assessment should be undertaken in line with the requirements of the latest version of PAS2035 for fabric improvement measures (also see previous comments regarding PAS2030 requirements).
In our ECO Demonstratio Action trial, Airex Floorvent was shown to increase air tightness by an average of 9% across the sample of 115 properties. This factor should be taken into consideration in the assessment of the overall ventilation of the dwelling.
In such an assessment, note that Airex Roomvent can form part of a background ventilation scheme to meet the PAS2035 and Building Regulations Part F requirement in a retrofit design.
Sub-floor ventilation
53. The durability of suspended timber floors is in most circumstances dependent on there being adequate and suitable cross-flow ventilation to the void below. The ventilation must be effective and unobstructed by any new materials, debris, or other detritus material.
As Airex Floorvent has a greater ventilation area than conventional air bricks, ventilation capability is enhanced by replacing these air bricks with Airex. As in the note above, cross-flow is desirable where possible, but if it is not possible Airex can mitigate risk through its monitoring and reporting of the void conditions.
There is some confusion around this requirement, with some in the industry interpreting “unobstructed” as meaning a need for “continuous” ventilation. However, the requirement here is that effective ventilation is not blocked by new materials (such as installed or stray insulation materials) or debris in the underfloor space (our installation guidance requires the removal of such debris).
Airex provides more effective ventilation than existing air bricks but controls that ventilation to reduce heat loss. Effective ventilation is provided as required based on internal and external environmental conditions monitored by the system.
Airex Floorvent continuously monitors the sub-floor void so that effective ventilation can be demonstrated and remedial action taken early if there are potential risks. In other words, Airex can help define and confirm what “adequate” and “suitable” ventilation means for properties re it is installed and help contribute to a greater understanding of this poorly studied part of homes.
54. When assessing the effectiveness of any sub-floor ventilation it is paramount that an inspection takes place of the floor levels externally in relation to the internal finished floor level. External works may have been undertaken since the property was originally constructed, such as new pavements, decking, soft landscaping or disabled access ramps. These may result in the air bricks and other vents becoming obstructed. Raised external ground levels if caused by soil or soft landscaping should be carefully reduced to restore full cross-flow. Where this is not possible, the use of telescope vents may provide a technical solution to maintaining the required ventilation.
Airex recommends following this guidance in the inspection and remediation of ventilation when installing Airex Floorvent.
Airex Floorvent can be fitted into the outer port of periscope or telescope ventilators if these are required and this will provide the same heat loss reduction and ventilation as if replacing conventional air bricks.
55. For the purposes of this guide, and without robust research having been undertaken in this area, the default requirement for ventilation for sub-floor voids will be the requirements set out in Part C 2013 of the Approved Documents for England and Wales, and its equivalent in Scotland and Northern Ireland. This requires that a ventilated air space measuring at least 75mm from the ground covering to the underside of any wall plates and at least 150mm to the underside of the suspended timber floor (or insulation if provided).
See notes on Part C compliance above. Through its data collection from 1000s of installations, Airex is building what is probably the world’s largest dataset of underfloor void conditions. Independent analysis of over 4 years of data so far shows that the Airex system does not lead to any significant increase in humidity in the underfloor void of properties where it is installed and that seasonal variation dwarfs any measured variability. We look forward to working with research partners to support further robust research to enhance understanding and future guidance.
56. In the case of a floor being considered for a thermal upgrade, it should be assumed that any measurement should be taken to where it is anticipated any insulation would finish, in relation to the ground covering. Two opposing external walls should have ventilation openings placed so that the ventilating air will have a free path between opposite sides and to all parts. The openings should not be less than either 1,500mm²/m or 500mm²/m² of a given floor area, (whichever gives the greater opening area). Any pipes needed to carry ventilating air should have a diameter of at least 100mm, and all ventilation openings should incorporate suitable grilles which prevent the entry of vermin to the sub-floor (but do not resist the air unduly).
This guidance is in line with the requirements of Part C of Building Regulations as noted above.
57. If floor levels need to be nearer to the ground due to the construction or alterations to external ground levels, then ventilation can be provided through the use of offset (periscope) ventilators that are rated to meet the requirements set out above. This requirement may require the addition of new airbricks or vents to meet the standard or if a more serious blockage, such as a house extension, has obstructed the cross-ventilation paths.
Airex installation does not require any modifications to floor levels. However, as noted above, Airex Floorvent can be fitted into the outer port of periscope or telescope ventilators if these are required and this will provide the same heat loss reduction and ventilation as if replacing conventional air bricks.
If new air bricks are required to provide cross-ventilation paths, Airex Floorvent can be installed as a new air brick and the existing air bricks also be replaced for full performance.
58. It should be noted that suspended ground floors were occasionally constructed without ventilation paths below, although not common practice. If it is noted during any inspection that the timbers and support walls are relatively dry, this may indicate that conditions are stable and therefore careful thought must be given to the effectiveness of adding insulation in these circumstances.
59. It is not unreasonable to assume that these stable conditions may have been helped by ventilation through board gaps to the room above. Under these circumstances, the addition of insulation may significantly obstruct this ventilation, and the addition of new ventilation paths below the floor may therefore be necessary, including through tassel walls (where present)
Unlike underfloor insulation, Airex does not block ventilation through the floorboards. This may assist ventilation when there are insufficient paths in the underfloor, as the path through the floor is still available.
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