building envelope insulation-by himanshu agrawal

7/30/2019 Building Envelope Insulation-By Himanshu Agrawal

http://slidepdf.com/reader/full/building-envelope-insulation-by-himanshu-agrawal 1/6

Pg 1 of 6

BUILDING ENVELOPE INSULATION A KEY TO ENERGY S AVING & SUSTAINABLE DEVELOPMENT

Author: Himanshu Agrawal

ABSTRACT:Buildings across the globe consume 60-70% of the total electricity generated and are a major contributor to the greenhouse gases. The maximum share of this energy usage is in conditioning (heating or cooling) the building interiors. In India, which has a tropical climate, insulation of building envelope would result in major energy saving and minimizing the greenhouse gas emissions whichwould contribute to a green and sustainable development. This paper dwells on the various aspects of “Total Insulation” of building envelope that includes moisture insulation (waterproofing) and thermal insulation.

INTRODUCTION:It is estimated that across the total life-cycle of a building, the design and construction of a commercial

building constitutes just 20-30% of the overall cost; the rest comprises of operations and maintenancecosts. Hence, it is important to actually consider how the high cost of operating can be reducedsubstantially.

Today’s modern buildings – marvels in terms of architecture and technology – have led to an adverseimpact on the environment. Buildings are responsible for more than half of harmful greenhouse gasemissions in most major cities of the world.

The maximum energy demand 50-70% in a building is for conditioning (heating or cooling) theinteriors. This major energy demand in a building is due to “Building Envelope” which contributes to60-75% of the heat gain/loss. Recognizing the need to save energy and minimize green house gases,efforts are being made to increase the awareness and importance of reducing energy loads in a

building. Insulation of building envelope has become one of the key practices across the globe toeffectively manage heat incidence in the buildings and save on the high energy cost.

For roofs, both LEED-India and GRIHA advocate over-deck insulation as against the conventionalway of under-deck insulation; green credit points for building envelope insulation are credited for over-deck roof insulation.

In over-deck insulation, a thermal insulation with waterproofing is provided over the RCC as a barrier against direct solar heat on RCC roof slab. This prevents the RCC slab from heating up. Theconventional method is under-deck thermal insulation by using methods like false ceiling or extrudedpolystyrene. However its effectiveness is always a question since the thermal barrier is providedunder the RCC roof slab. Some heat passes through the under-deck insulation and decreases the



Pg 2 of 6

comfort level of the room. If the building is air-conditioned, this heat leakage increases the AC load.Hence it can safely be concluded that over deck insulation has its own advantages against under deck.

BUILDING ENVELOPE INSULATION – A HOLISTIC APPROACH:

I. ROOF INSULATION (OVER-DECK):

This type of insulation has to take a composite approach to provide –

• Thermal insulation

• Waterproofing and

• Slope built-up.

Brick bat Coba:The love of the Indian construction industry is the use of brick bat coba for roofs. This system consistsof putting brickbat on flat roofs to give a slope and then grouting the same with cement mortar admixed with some water proofing compounds. This is mostly finishedwith IPS topping with a tile pattern cut into the top to form crack inducer joints to prevent cracks from appearing; alternatively China mosaic isdone as the top wearing course. There is a myth that brick bat cobaoffers waterproofing and also insulation against heat. Nobody can rightly

call it a waterproofing material because it is porous and allows the entryof water into it very easily, serving as a reservoir. Neither is it, by anystretch of the imagination, a thermal insulation product. In fact the heatabsorbed by brick bat coba it is the same as that absorbed by concrete.

Advantages:

• Provides Slope: This system provides an excellent slope for the water to drain away. As water does not accumulate and as it has a certain capacity to absorb water, thereis no leakage.

Disadvantages:

• Impose Dead Load: This system puts unnecessary dead load on the structure.

• Cracks Up: Brick bat coba cracks up due to temperature variation and movementsdue to thermal stresses. Once cracks appear, water travels below the coba and

leakage starts. It is very difficult to trace the inlet point and repair it.• Difficult to Dismantle: Some parts of the coba stick so well to the concrete that an

attempt to dismantle the system may damage the slab.

Tar Felt / APP Membrane:This system uses layers of tar interspersed with various forms of reinforcements to hold the layer together and prevent cracking to provide impermeable layer betweenthe water and the surface to be protected.

Advantages:

• Cheap

• Suitable for AC sheet roofing

Disadvantages:

• Not UV Resistant: Tar/Bitumen - the binder in the system disintegrates on contactwith 'UV' radiation leading to biodegradation of reinforcement leading to collapse of the system.

• Debonding: Vapour trapped inside exerts vapour pressure resulting in debonding of the membrane.

Mud Phuska:In this conventional system of providing thermal insulation, a 10 cm layer of puddled clay mixed withgrass straw is applied in slope on a sand-bitumen waterproofing layer. This layer is consolidated andplastered with 13 mm of cow-dung mortar. Tile bricks are laid flat on plastered surface and the jointsare grouted with cement mortar.



Pg 3 of 6

The Thermal and surface properties of mud phuska are as below;Density = 1622 kg/m

3

Thermal conductivity = 0.750 W/mKSpecific heat capacity = 0.88 kJ/kg-K

[Reference: SP 41, Handbook on functional requirements of building (Other than industrial buildings), Part 1-4, Bureau of IndianStandard (1988)]

The traditional and conventional systems of waterproofing and thermal insulation in India worked well

for ages to suit the Indian construction and economics. However, these systems do not have a longlife and require frequent maintenance. These systems also do not suit the complicated site dynamicsof today’s construction and do not offer insulation values to comply to ECBC norms.

TOTAL INSULATION CONCEPT:To provide over-deck roof insulation that complies to ECBC requirements, a composite built-up isrequired which consists of a thermal insulation material with high “R-value”, coupled with a suitablewaterproofing and complete with a light weight material for the slope built-up for water run-off. Atypical schematics of total insulation built-up would be as shown in the diagram below;

ROOF INSULATION COMPONENTS:

1. WATERPROOFING

• MASTERSEAL ®

550 EL: Two-component, flexible, cementitious, polymer modified, brush-applied, water-proof coating can be applied directly on the concrete substrates and provideswatertight sealing of pores and dormant cracks in the substrate.

• SONOSHIELD ®

HLM 5000R: Single component, moisture curing, liquid applied, modified

polyurethane, Elastomeric water-proof membrane has >600% elongation.

• MASTERPREN ®

TPO: Single-ply, preformed, TPO water-proof membrane is a single-ply, water-proof membranes available inglass/polyester reinforced versions. MASTERPREN

®TPO can be

selected and designed on the basis of the roof overlay like green roof,podium, ballasted roof, metal deck. It is also capable of re-roofing theexisting leaking roof without dismantling the existing system.

• CONIROOF ®

: Spray-applied, PU water-proof membranes consists of low-modulus PUmembrane which is best in class for high elasticity and high adhesion capability which makes

Tile Grout Stone Tile/China

Beddingmortar

Coving using,Polymer

Modified Mortar

MASTERSEALWaterproof coating

Peripor / Elastopr Board/

PU Spray Foam

Insulation

THERMOCRETEEPS Bead Mortar

Overlay

MASTERSEAL

300HProtective

coating



Pg 4 of 6

it perform on variety of substrates like natural stones, bricks, metal sheets, marine ply andeven old/leaking bitumen membranes and PVC membranes.

2. THERMAL INSULATION:

• Peripor Board: The Water-resistant insulation.When building components are subject to pressure and moisture, the insulating materialsused should absorb as little water as possible since water

absorption has a significant detrimental effect on thermalinsulation. Peripor Board has been developed specifically for such applications. It is a high-quality thermal insulation productwith a water-resistant bead surface. This combination of properties greatly reduces water absorption and is thus suitablefor use in the tropics.

• Elastopor Board: Thermal Insulation PUR Board.Polyurethane Resin (PUR) based thermal insulation boards offer best in class insulationperformance. Higher densities make the boards tough and can be used in trafficked systembuilt-ups. Elastopor Boards are specially designed with skin layer on both faces, making itresistant to water ingress and long lasting.

• MASTERSEAL 755 SPF: Spray applied PU foam for thermal insulation is a two component

system, spray applied at site. This allows spray application on complex substrate shapes andconfined spaces, besides it lowers materials transportation cost.

A comparative graph of “R-value” with the above insulation materials as compared to brickbatcoba is shown here:

0

0.5

1

1.5

2

2.5

3

150mm RCC 150mm RCC+

100mm

BrickbatKoba

150mm RCC+

50mm

PERIPOR

150mm RCC+

50mm

Elastopor

R V a l u e , s q . m . K

/ W

3. SLOPE BUILT-UP:

• ThermocreteTM

:

A need is felt for a suitable material to replace brickbat coba for thepurpose of making slope/fall on the flat roof slab for the purpose of water run-off and also for the protection of waterproofing and insulation layers.

Thermocrete™ is an excellent replacement for brickbat coba on a roof built-up due to its light weight, high thermal insulation, better compressive strength, low water absorption and ease of installation.

Thermocrete™ is site-batched light weight trowelable concrete usingselective grades of expanded polystyrene beads (EPS) as thermalinsulating aggregates. It combines the construction ease of concretewith the thermal insulation properties of EPS and can be used for a verywide range of application where lighter loads or thermal insulation or both are desired.



Pg 5 of 6

Comparitive charts for Dead Load & Thermal Resistance “R” for 150mm thick overlay:

II. WALL INSULATION:

Though a major contribution to heat gain in a building is from walls, still, wall insulation has never been of much concern or simply, wall insulation has just been neglected. Some traditional ways of

providing thermal insulation to the walls have been in the form of using light coloured stone tiles on exteriors to minimize sunlight,double-wall with air cavity, cavity wall with insulation material as infill,insulating panels on interiors, etc. However, each of these methodshave their own disadvantages as apart from not offering a highthermal insulation, they have the problem of rain water seepage,water filling the cavity, poor indoor air quality, decrease of valuableinternal space, etc.

All these drawbacks are avoided by using “External Insulation &Finishing System” (EIFS) on the walls.

• SENERGY EIFS system consists of Neopor insulation board, adhesive for fixing insulationboard to the substrate, anchoring system for fixing the reinforcing mesh in place over the

insulation board and base coat which provide the mineral substrate for the application of thetop coat. The top coat provides the long lasting aesthetics and finish to the system. Based onthe insulation performance warranted, the type and thickness of insulation board is designed.

Sections of EIFS on a framed sheathing and on a concrete/plastered brick surface are asshown below

EIFS offers the following benefits which are not offered/matched by other wall insulationmethods;

EIFS has superior energy efficiency by reducing heat transmission and helps inreducing HVAC load.

The adhesive coat, base coat & top finish coat are polymer based and provide highdegree of water resistance to the wall.



Pg 6 of 6

It can be applied to new & existing structures. External Location; Virtually Seamless – Reduced Air Infiltration Offers design flexibility, shapes, colors and textures Flexible and Lightweight Material Little Routine Maintenance It is the only solution for insulating existing buildings.

Neopor Insulation Board: This high performance thermalinsulation board is used in SENERGY EIFS.

Contains Infrared absorbers/ deflectors 20% higher energy efficiency then EPS Flame retardant grade (B2) K value of 0.032 W/m.K Free of CFC, HCFC or HFC

CONCLUSION:Buildings consume a major portion of electricity generation and put a lot of stress on the society atlarge in terms of electricity shortage and emission of greenhouse gases. With the fast depleting fossilfuel reserves and ever increasing electricity prices, it is imperative to adopt energy saving measures.It is necessary for the construction industry to adopt green measures which would benefit their ownpocket and the society. We should adopt workplace strategies to meet sustainability goals whilereducing overall occupancy costs. Today, global companies are offering to the Indian constructionindustry, new products, technology, systems and application expertise as a one-stop 360

Osolution for

the building envelope insulation. Adopting Green Building practices will substantially reduce or eliminate adverse environmental impacts and improve upon existing unsustainable design,construction and operational practices.

For additional information on Building Envelope Insulation, contact author at BASF India Limited,Construction Chemicals Division, Plot No 37, Chandivali Farm Road, Chandivali, Andheri East, Mumbai -400 072, India.Phone: +91 22 2858 0365 Fax: +91-22-2847 8381Email: [email protected]

About the Author:

Himanshu Agrawal did his graduation in Civil Engineering from RegionalEngineering College – Surat (South Gujarat University) in 1991. He has a richexperience of industrial project management and worked with companies likeUnited Phosphorus Ltd., Metrochem Industries Ltd., Cyanamid India Ltd. & BASF

India Ltd. He has also worked in Sales with BASF Construction Chemicals (India)Pvt. Ltd.

Himanshu Agrawal heads the Marketing & Business Development of Sustainable Building Solutions forSouth Asia with BASF India Ltd. to develop and promote Green and Sustainable products, technology& systems for the construction industry.

building envelope insulation-by himanshu agrawal

Documents