Installing PIV instead of cMEV, dMEV or MVHR is compliant with PAS 2035 but
involves more risk. Since those risks have not yet been properly evaluated, the
Caution principle in BS 5250 suggests that PIV should not be specified. This is why
the Retrofit Academy does not recommend PIV. We recommend listening to the
advice of your Retrofit Coordinator, who is there to protect the client’s / householder’s
interest and help you manage risks. Ignoring the advice of the Retrofit Coordinator
could be seen as inappropriate and irresponsible.
If you want to monitor energy use, a smart meter is recommended. For internal air
temperature and relative humidity Tiny Tags and Hobos or a Switchee can capture
this data for you. If you are looking for a specialist to instal and monitor, make sure
you know what you want the information for as monitoring can be expensive. Most
monitoring is done by academic groups, but some of the technical consultancies
(e.g. NBA Tectonics, MES Building Solutions) also provide monitoring services.
Permanent monitoring via devices such as Switchee is the most economical method.
Yes. The retrofit assessor
will need to markup opening
windows as part of the
ventilation assessment (this
is likely to be in the new BS
40104 standard for retrofit
assessment). The only way
that a window will provide purge ventilation
is if it is capable of opening. There is a need
to understand the ventilation provision in the
context of that property.
There is no way of doing it respectively, and because of the fact that there is a
requirement for Whole House Surveys on every dwelling. There is a requirement
to identify all the services, all the defects, and anything else that may not make
that building retrofit ready. And then you would have issues over the warranties of
the external material, that if you then needed to put ventilation in and ventilation
pores, and actually started coring holes in the external wall insulation, you would
then void any warranty of that material, because it would be done retrospectively
and understand access is a real issue. One of the reasons that PAS come out was
because of this, people weren’t surveying internal properties correctly, they weren’t assessing the
ventilation, they weren’t assessing the condition.
Fire regulations concern the protection of structures by compartmentation, to
restrict the spread of fires. Part B of the building regulations provides guidance on
this, with the key requirements in table B4. This indicates that what is important is
the compartmentation between other habitable properties, or mixed use where you
have a residential over a commercial purpose. If you’re the floor of an upper floor flat
that is above the lower floor flat, we would question why you would be doing under
floor insulation anyway, because there is no heat loss. (unless you are talking about
This depends on the status
of ownership of that ginnel
and what is its purpose? Is
it to provide access to bins?
Or to other properties? You
also have to consider access
for people who might be
wheelchair disabled. It may well be that the fire
service needs that ginnel to access the rear of
the property because of the layout of the estate.
If you don’t do it, you then have a whole flank
wall, which is introduced in a thermal bridge,
which probably has got the internal staircase
across it, because of the way that those types
of properties are laid out, you’ve then got big
thermal bridging issues or the challenge of
trying to insulate the wall internally. These are
the initial things you should be thinking of.
The Internal Wall Insulation Best Practice Guide says that that is acceptable
provided that there is continuous ventilation and adequate heating in the kitchens
and bathrooms. We think that internal wall insulation should always be continuous,
and it should be done in conjunction with kitchen and bathroom replacement.
However, if you follow the BEIS guide, then that is acceptable as this is then deemed
compliant with PAS 2035.
Predetermined measures are
not compliant with PAS 2035,
the measures are determined
by the assessment, the
evaluation and the medium term plan. So, even if that
is what is in the bid it’s not necessarily a
compliant solution. The real answer here is,
‘it depends’. There is a lot of things we don’t
have there. It depends on what poor condition
means. What is the material? What is the exact
construction of the building?
Yes, you do have to meet ADF in anything that you do to meet building regulations. If
you are putting new IEV fans in, it is reasonable to assume that the rated ventilation
rate of the fan is what is listed on the box. If you are using an existing fan, it might be
an idea to check that the fan is suitable, though the PAS 2035 does say if there is a
fan in place and it’s working, that is deemed an adequate ventilation system. If you
want to check the performance of a fan, note that a calibrated anemometer it is not
going to give you flow rates, it’s going to give you air speeds. To get the flow rates you
need to use a hood anemometer.
If the insulation measures in the dwelling are intended to reduce the air permeability below 5 m3/m2h
at 50 Pa, or they might do accidentally or unintentionally, then you have to upgrade to continuous
ventilation. The only time that you are asked to do a pressure test (by PAS 2035) is if you think the
air permeability is not below 5 and therefore you don’t want to move to continuous ventilation. PAS
2035 gives you the option of doing a pressure test to demonstrate the air permeability is above 5
and therefore you can stick with intermittent ventilation instead of continuous ventilation.
This doesn’t only apply to wall
insulation measures; it is any
element that you happen to
be insulating. The highest
risk is going to be where you
are insulating internally rather
A possible solution is for the
fan to be taken up through
the roof. Where there is a
habitable room above (i.e., in
a two-storey property) another
option is to apply ducting and
0.6 PAS 2035:2022 Amendment 1
Both PAS 2030 and PAS 2035 have incorporated minor changes in response to early
application of the standard in the retrofit industry. The main amendments are:
• Removal of the Retrofit Advisor role pending improved qualifications in this area.
Retrofit advice has not been removed from the PAS 2035 process and is delivered
by other retrofit professionals.
• Clarity on when a ventilation assessment is to be undertaken. [This is just
clarification that the requirement applies to Path A, as well as Paths B and C]
• Explicit inclusion of airtightness as part of insulation retrofit in both PAS 2030 and
• Clarity around stage-by-stage retrofit and how to manage risks in between stages.
If there is a cavity, the purpose of the cavity is to ventilate the wall to remove moisture,
therefore it is a thermal bypass. So, putting EWI on an unfilled cavity wall however
narrow the cavity is, creates a thermal bypass which reduces the effectiveness of
the EWI. So, it makes sense to fill the cavity as well as applying EWI, then you have
even better thermal performance. If you can’t fill the cavity there is a route offered
by SWIGA where you can seal it so that it’s no longer ventilated. The guidance and
requirements for the cavity bypass when undertaking EWI is available on request
There is guidance available in
the form of a flow chart which
is contained in the BEIS IWI
Guide, page 34: click here
The Property Care Association (PCA) recorded this webinar which may be helpful:
click here to watch on YouTube