THERMAL INSULATION AND LAGGING HVAC CLADDING



الحمد لله والصلاة والسلام على رسول الله وعلى آله وصحبه أجمعين 

THERMAL INSULATION AND LAGGING HVAC

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General Requirements

Thermal insulation shall be of approved material with thermal conductivity 
not higher than 0.29 Btu/Hr/Ft2/F inch thickness measured at an average 
temperature of 100 F. Thermal insulation shall be non-corrosive to the metal
water repellent, sustenance to vermin and easily cut and fitted to shape during application
The insulation should be resilient and retain its original shape
The insulation shall be provided with approved fire retardant vapour barrier
jacket to prevent the moisture penetration to the insulation
Vapour barrier shall also be applied to all joints and edges

The insulation shall be fixed on to the metal surface by means of an 
approved adhesive compound that has no corrosive effect on the metal 
and thoroughly applied to the metal surface and insulation
The insulation shall be carried out by skilled labourers and before thermal
insulation is applied, all metal surfaces shall be thoroughly cleaned and treated
with approved corrosion inhibitors

Piping Insulation

The insulation shall be secured to the piping by adequate number of 
non-corrodable straps ¾” width at a center distance not more than one foot

The straps shall not in any case cut the insulation or the vapour seal
Wires shall not be acceptable

Insulation Material Thickness

Insulation material shall be Fiberglass 6 lb/Ft³ & shall have the following thickness

Pipe Size Up to 2” dia 2½” – 6” dia 8” dia & above

Chilled / Hot Water Pipes exposed to Sun 1” 2” 3”

Chilled/Hot Water Pipes in non-A/C areas 1” 1½” 2”

Chilled / Hot water pipes in A/C areas 3/8” 1” 1½”

Condenser Water (Cold) pipe from cooling tower to condenser exposed to sun 1” 

Condensate drain pipe 3/8” 5/8”

All pipes running inside the A/C Plant room, A/H unit rooms and other 
machinery rooms also inside the piping shaft or were they are exposed 
to view shall be covered with heavy gauge “not less than 22” aluminium sheet
and in any case the designation and direction of fluid flow shall be suitable 
marked on the surface at intervals. Weather and water proofing treatment to 
be carried out prior to cladding

Duct Work Insulation

The thermal insulation used shall confirm to BS 5422: 1977 – BS 5422: 2009

The thermal insulation shall be made of fiberglass material with reinforced 
aluminium foil external coating, factory applied with resin bonded internal 
layer to give flat and resilient surface. The insulation of all duct works exposed 
to outside and those in plant rooms shall be rigid slab type and for remaining
ducting flexible blanket type

Thermal conductivity shall not be more than 0.29 Btu/Hr. Sq. Ft. per inch thickness 
measured at an average temperature at 100° F. The thermal insulation shall be non-corrosive

The insulation shall be provided with fiber retardant
vapour barrier jacket to prevent moisture and penetration
Vapour barrier shall also be applied to all joints and edges

The insulation shall be applied to metal surface by means of 
approved non-corrosive adhesive compound.
The metal surface shall be treated with corrosion
inhibitors before the application of insulation

The density of insulation shall be minimum 1.5 lb./cu. ft. for flexible 
blanket type and 3 lb./cu. ft. for rigid slab type and thickness 

All duct works exposed outside and those in plant 
room shall be insulated with 2” outside insulation

Duct works inside air-conditioned spaced shall be 
insulated with one inch thick outside insulation

h. Insulation shall be secured to duct work with 2” x 2” G.I. sheet metal 
strips of 22 gauge fixed to corners and tightened with wire 6” intervals
The strips may be suitably grooved to take the wire fasteners

In addition, all duct works exposed to outside be cladded with 24 gauge GI sheeting 
and shall be treated for water proofing prior to cladding, i.e. wrap 
the insulation with 0.5mm thick polyethylene sheet and secure the adhesive
All the duct works in plant room shall be finished with 8 Oz. Canvas
with 2 coats of fire retardant and water proof paint.

All external duct cladding shall be painted with one coat of primer suitable for
galvanized surface and two coats of final paint suitable for external application
Colour of paint should match the building and approved by the Engineer

Acoustic Duct Lining

Internal duct lining for acoustic insulation where applicable shall 
not be less than 25 mm. thick fiberglass mat faced, flexible blanket
of fine fibers with securely bonded surface mat coated with black 
neoprene or approved equal. Lining shall be applied with 100% coverage
of fire resistive approved adhesive compound and mechanical fastenings 
according to the manufacturer’s instructions. Acoustic lining shall be 
cleared 20 cm. on each side of the duct heater where applicable
Duct lining density shall be 24 kg/cubic meter

في أمان الله 

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