Welcome to the FAQ’s

This section lists some of the many questions Retrofit Academy staff and tutors have been asked over the years.

An installer has raised the question of whether they can install a PIV system instead of IEV in wet rooms. I’m aware that The Retrofit Academy does not recommend the use of PIV however if the proposed PIV system complies with PAS requirements, can the RC prevent the installer from proceeding?

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.

Are there any recommended monitoring equipment installers for sensors and loggers for internal air temperature, relative humidity and energy usage?

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.

Looking for guidance on purge ventilation: Is it mandatory to provide all windows showing purge ventilation and is this documented anywhere to show surveyors?

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.

We’re working on several large-scale social housing projects. 400 units per project is an example. And are experiencing issues in terms of gaining access to a small percentage of the portfolio around 5%. Namely, due to vulnerability, health, social issues, etc. We’re trying to work with the spirit of the past and gain access to every dwelling. But this is a real issue across most of our projects. What opportunities are there still to proceed with external fabric works? For example, EWI, compliantly, under the PAS. Would an archetype appraisal be sufficient short term with a view to carrying out an internal assessment to verify condition and ventilation improvements at a later date? Perhaps during a void relet, kitchen replacement works, etc?

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.

Can you please clarify when building regulations apply to underfloor insulation and when it is a requirement to overboard the insulation with a fire rated board to achieve 30-minute fire protection? It is very difficult to pin down the exact rules around this and it is not explicitly detailed in the BEIS UFI guide.

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
acoustic insulation).

Potential EWI of ginnels (narrow alleyways) between terraced properties – installers have concerns as to feasibility of doing this. What are issues to consider / resolve?

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.

One Local Authority has an installer trying to convince them that they don’t need to install insulation in bathrooms and kitchens of houses and that thermal bridges won’t be an issue for the rest of the dwelling. Is this correct?

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.

A council client has started Path C scheme on non traditional PRC dwellings with predefined EWI measures. The assessment has identified cavity infill insulation in poor condition – a EWI systems installer has advised that it is fine to leave these in situ and install EWI over the top – however assessor thinks it should be extracted as it was installed some time ago so will have a different lifespan than the EWI and shouldn’t have been installed in the first place to PRC construction type. What do we advise?

Predetermined measures are
not compliant with PAS 2035,
the measures are determined
by the assessment, the
improvement option
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?

There seems to be a lot of existing IEV fans being left in homes where fabric measures are being lodged with Trustmark as PAS2035 compliant, anecdotally without any air pressure test being completed to ascertain whether the air permeability of the building envelope is above or below 5 m3/m2h at 50 Pa after the installation. My understanding is that if the air permeability is not known, you must replace IEV with an alternative such as continuous MEV or PIV, as IEV “shall be assessed as inadequate” (C.2.4). This is also explicitly stated in C3.3 and C3.5. Please confirm if my understanding is correct? If so, what will Trustmark look to do with all of the previous non compliant measures? As a follow up to this, if an air pressure test is completed post installation and it can be evidence that the air permeability is above this threshold, does PAS2035 require all IEV fans to be tested using a calibrated anemometer and if so, does the tester need to hold a suitable qualification (NICEIC etc) to ensure that the extract rates meet those required in Approved Document F? Or is it acceptable to just assume that the fan is designed to extract at the required rate for the wet room it is in and that the in-situ extract performance is actually still delivering this minimum required rate? Presumably where an air pressure test has been completed, if brand new IEV fans are fitted with known extract rates that meet ADF, the RC can assume compliance without the need for any testing of the fans? (Assuming it is needed)

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.

What measures would trigger a condensation risk assessment in accordance with BS5250? I believe it is all insulation measures, however, this has been challenged with only wall insulation measures.

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
than externally.

If a mid-terrace property with a kitchen to the rear elevation has no suitable wall space to install a new IEV fan due to window and door sizes/positions, what options are available? Other than installing an unsightly window extractor fan, would it not be possible for this job to comply with PAS ventilation requirements?

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
extract horizontally.

What are the significant changes to the PAS that were made in February’s release?

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
PAS 2035.
• Clarity around stage-by-stage retrofit and how to manage risks in between stages.

Many homes have narrow cavities that aren’t suitable for CWI. What’s the best approach to insulating these walls with SWI? Does installing EWI with the cavity left unfilled create a thermal bypass and mean that the EWI is ineffective/pointless? Or is there a sensible approach using EWI?

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
from SWIGA.

LAD2/SWC IWI suppliers intend not to install in bathrooms and kitchens, claiming the installation would be PAS2035 compliant. Concern that partial IWI insulation of properties will create significant thermal bridging but client has limited technical experience to rebut the claims of the installer. Knowledge Hub/FAQs doesn’t provide any guidance – can the members help?

There is guidance available in
the form of a flow chart which
is contained in the BEIS IWI
Guide, page 34: click here

Any thoughts on using open cell spray foam on pitched roofs with sarking?

The Property Care Association (PCA) recorded this webinar which may be helpful:
click here to watch on YouTube

T: 0330 055 7629
E: info@retrofitacademy.org
A: Barn 4, Dunston Business Village,
Stafford Road, Stafford, ST18 9AB

Terms & Conditions 
Policies & Procedures

Copyright © 2022 The Retrofit Academy. All rights reserved

Website by
Fill out the form below to download the guides