flat roof parapet construction detail

jimmy_t

Quinn have an accredited detail online showing a flat roof parapet with the insulation wrapping around the quinnlite blocks. Is this insulation necessary? The detail isnt repeated at the footings so why is it necessary here?

sydthebeat

jimmy_t wrote: »

Quinn have an accredited detail online showing a flat roof parapet with the insulation wrapping around the quinnlite blocks. Is this insulation necessary? The detail isnt repeated at the footings so why is it necessary here?

"necessary" is a subjective word and one for your architect.


The reason theres a difference is because ground is warmer than the air at roof level, therefore heat loss is less at footing level. eg it could be -5 at roof level and 5 degrees at footing level at the same time.

thats why pipes buried deeply are less likely to burst when compare to those exposed in the open air.

jimmy_t

Have you ever found the benefit of this detail to outweigh the cost complexity?

BryanF

Part L calls for thermal continuity. How would you propose to achieve this?

Metric Tensor

Just to play devils advocate - will the psi value change much if you use that detail except substitute the Quinnlite block for a standard block?

I don't know the answer so I'm only throwing it out there as something to be considered.

Also that diagram considers thermal behaviour but leaves all sorts of questions regarding structure and weather tightness.

I'd definitely be consulting your Architect, Engineer or Technician about it!

Edit: Just to clarify I am talking about the parapet detail shown in the OP in this post. I am aware there is two simultaneous conversations going in this thread.

BryanF

DETAIL 1.01b, 2011

http://www.housing.gov.ie/sites/default/files/migrated-files/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad%2C18751%2Cen.pdf

Please note the detail your talking about is one of the (very average government details) minimum building standards and have been for ~10years

jimmy_t

BryanF wrote: »

Part L calls for thermal continuity. How would you propose to achieve this?

currently the spec is a 200mm pumped cavity, 2 courses of quinnlites on the parapet and 150mm rigid PIR on the roof. Would this not be considered thermally continuous? It is a similar detail to ACD 1.20, 2011 except that suggests a insulated upstand instead of AAC blocks

jimmy_t

BryanF wrote: »

DETAIL 1.01b, 2011

http://www.housing.gov.ie/sites/default/files/migrated-files/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad%2C18751%2Cen.pdf

Please note the detail your talking about is one of the (very average government details) minimum building standards and have been for ~10years

The footing detail we are using is very similar to this, 200mm pumped cavity which extends an additional block below the quinnlite, one row of quinnlites and 165mm Thermafloor below screed. If this is out of date what is now considered best practice? The detail on the Quinn website doesnt show much advancement beyond using 2 rows of Quinnlites?

jimmy_t

Metric Tensor wrote: »

Just to play devils advocate - will the psi value change much if you use that detail except substitute the Quinnlite block for a standard block?

I don't know the answer so I'm only throwing it out there as something to be considered.

Also that diagram considers thermal behaviour but leaves all sorts of questions regarding structure and weather tightness.

I'd definitely be consulting your Architect, Engineer or Technician about it!

Edit: Just to clarify I am talking about the parapet detail shown in the OP in this post. I am aware there is two simultaneous conversations going in this thread.

Weather tightness is paralon above insulation and 500ga polythene membrane below. This is sitting on screed on hollowcore designed by structural engineer so I assume that bit is right.

BryanF

jimmy_t wrote: »

currently the spec is a 200mm pumped cavity, 2 courses of quinnlites on the parapet and 150mm rigid PIR on the roof. Would this not be considered thermally continuous? It is a similar detail to ACD 1.20, 2011 except that suggests a insulated upstand instead of AAC blocks

Show us the detail? That sounds like a good spec

BryanF

jimmy_t wrote: »

The footing detail we are using is very similar to this, 200mm pumped cavity which extends an additional block below the quinnlite, one row of quinnlites and 165mm Thermafloor below screed. If this is out of date what is now considered best practice? The detail on the Quinn website doesnt show much advancement beyond using 2 rows of Quinnlites?

proprietary PIR blocks instead of quinlites
Better variation if quinlites from Europe such as ytong which can almost be used on their own
insulated ring beam (passive type insulated systems etc)

The levels of insulation your proposing is pretty good though?

Why skimp in the roof junction insulation?

jimmy_t

BryanF wrote: »

proprietary PIR blocks instead of quinlites
Better variation if quinlites from Europe such as ytong which can almost be used on their own
insulated ring beam (passive type insulated systems etc)

The levels of insulation your proposing is pretty good though?

Why skimp in the roof junction insulation?

I dont know why the roof insulation is less than best practice, it has been thermally modelled but I never saw the results just a green light from Arch and modeller. The brief is to passive certify so Im just maybe surprised it has been achieved with "standard" details.