You should have a chat with your local planning officer and fire officer.
The planner to make sure that no planning issue arises when replacing the windows, particularly is this is a listed or historic building.
The fire officer to confirm that the information given below from the DOEHLG website is current up to date.
For your guidance, there, and non-definitively, herewith a section from TGB B from the DOEHLG website.
http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,1640,en.pdf
Windows for Escape or Rescue
1.5.6 Windows may provide an alternative means
of escape or may be used for rescue purposes in
dwelling houses of limited height. As an alternative, a
door which gives direct access to a balcony or roof,
which is suitable for rescue by ladder or for escape
may be used. Where provision is made in this subsection
for windows for these purposes (see
paragraphs 1.5.2, 1.5.3, 1.5.7.6 and 1.5.8.2), such
windows should comply with the following:
(a) The window should have an openable section
which can provide an unobstructed clear open
area of at least 0.33 m2 with a minimum width
and height of 450 mm (the route through the
window may be at an angle rather than straight
through). The opening section should be capable
of remaining in the position which provides this
minimum clear open area.
(b) The bottom of the window opening should be
not more than 1100 mm and not less than 800
mm (600 mm in the case of a rooflight) above the
floor, immediately inside or beneath the window
or rooflight. As an exception to the general
guidance in TGD K (Stairways, Ladders, Ramps
and Guards) that guarding be provided for any
window, the cill of which is less than 800 mm in
height above floor level, guarding should not be
provided to a rooflight opening provided in
compliance with this paragraph.
(c) In the case of a dormer window or rooflight, the
distance from the eaves to the bottom of the
opening section of the rooflight, or, where the
window is vertical, the vertical plane of the
window, should not exceed 1.7 m measured
along the slope of the roof.
(d) The area beneath the window externally should
be such as to make escape or rescue practicable.
For example,
(i) where there is a clear drop from a window in
an upper storey or attic conversion, the
ground beneath the window should be
suitable for supporting a ladder safely and be
accessible for rescue by the fire services or
others.
(ii) Where there is a roof, balcony or canopy
below a window, it should be structurally
adequate to support those using the window
for escape or rescue.
(e) The opening section of the window should be
secured by means of fastenings which are readily
openable from the inside and should be fitted
with safety restrictors. Safety restrictors can be
either an integral part of the window operating
gear or separate items of hardware which can be
fitted to a window at the time of manufacture or
at installation. Restrictors should operate so that
they limit the initial movement of an opening
section to not more than 100 mm. Lockable
handles or restrictors, which can only be
released by removable keys or other tools,
should not be fitted to window opening sections
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FWIW
ONQ.
