SRS Finlay Energy Saving Buildings: Usage of Thermal Blocks in Walls

Yireikan Khapudang, General Manager, SRS Finlay

The continuing need to conserve energy has resulted in mandated requirements for the thermal performance of construction. Since it is impractical to measure all buildings or building components and systems for thermal properties, simple and accurate methods to reliably predict thermal performance are necessary. Design professionals must estimate the energy requirements associated with all types of building systems, including masonry, to select appropriate systems and to provide for economical heating and cooling design.

Building design and material properties influence thermal performance and energy consumption for residential and commercial buildings. Insulated wall, floor and roof systems provide an innovative combination of excellent thermal conductivity, thermal mass and low air-infiltration. This practical combination of properties in one system provides an excellent thermal insulation material and permits peak energy usage in the building to be shifted to off-peak hours, thus reducing operation cost for building users and owners, improving comfort of living and reducing the demand on power generation facilities. One can look at Substantial reduction in air conditioning tonnage and huge savings in monthly electricity bills up to 40%. It is very economical for centrally air-conditioned buildings, public utility structures, government buildings, schools, hospitals, theatres, shopping complexes, and so on.

Thermal Blocks

Thermal / Dow STYROFOAM (XPS)/Polystyrene insulated blocks are made of concrete consisting of selected aggregate and cement with extruded STYROFOAM (XPS). The Polystyrene/STYROFOAM (XPS) is specially designed and placed symmetrically during the time of moulding the blocks at wet stage of concrete.

Thermal blocks are high load bearing, fire resistant, excellent sound insulation and high thermal efficiency building concrete blocks.

The most standard sizes of thermal blocks with cavities are

• Size 1: 400x200x200 mm (8")
• Size 2: 400x250x200 mm (10")

Thermal Values of the blocks recorded at 35°C and 60% R.H.

• U value: .362watt/m2 K
• K value: .037 watt/m K
• R value: 1.75 m2 K/ watt

Product Description

It is a STYROFOAM (XPS) sandwiched block where the STYROFOAM (XPS) is integrally locked symmetrically into concrete structure (incorporated at the wet stage of concrete itself) resulting in an excellent thermal insulation and bonding. This is a proven technology of two decades, widely used in Europe and Middle East.

F-24 C, SRS Finlay Egg Laying machines allow such arrangement in which profiled STYROFOAM (XPS) pieces are pre-fixed on the mould box where the semi dry mixture pours over the top. The profiled cut STYROFOAM (XPS) can be supplied by players like Dow chemical's who has started marketing the product in India extensively.

The use of block work allows structures to be built in the traditional masonry style with layers or courses of overlapping blocks. These cement hollow blocks are widely used for building infrastructure and require low maintenance. High dimensional accuracy and consistent finish make these blocks an ideal building material for both load bearing constructions as well as partition walls. These concrete hollow blocks are a better substitute to work faster to build a structure long lasting value.

Thermal Insulation

The concept of insulated building is not new in India as there are number of green buildings which are rated as environment-friendly with LEED certifications. Insulated building material such as auto cleaved aerated concrete blocks or STYROFOAM (XPS) sheet insertion in between the cavity walls is widely practiced in India. However, the Insulating property of thermal blocks are far superior to aerated blocks, as it provides 4 times more insulation in terms of “K Value – Thermal Conductivity.” Though this value may not be the total parameter for an Architect/Engineer for the design of an energy efficient building, it forms one of the important key factors along with other material characteristics like block density, strength, ambient temperatures etc.

While specifying the most efficient materials and fittings, there are three ratings used for estimating heat loss/gain: the K rating, the R value, and the U value.

• K Value – the lower the better (Thermal conductivity)
• R value - the higher the better (Thermal resistance)
• U value - the lower the better (Thermal Transmittance)

The difference in thermal performance between seemingly similar products can be dramatic, which is why it's so important to keep an eye on the R and U values. Normal 250 mm thermal concrete blocks have an R of 1.75 while an Aerated block will have an R of 0.46. A wall built of thermal concrete blocks will therefore insulate 4 times as much heat as a wall built of AAC blocks.

A brief comparison chart is shown below
Properties	Autoclaved Aerated Concrete Block	Dow’s STYROFOAM (XPS) Inserted Thermal Concrete Block
"K" Thermal Conductivity at 35°C and 60% R.H.	0.134 W/m.k°	0.037 W/m.k°
"R" Thermal resistance	0.46 M^2 K/W	1.75 m^2 K/W
Water Absorption	Low	Low
Average STYROFOAM (XPS) Density	N/A	26 kg/m^3
"U" Thermal Transmittance Value	2.13 W/m^2 K	0.36 W/m^2 K
Compressive strength of the Blocks	3-4 N/mm^2	7.5-10 N/mm^2
Density	550-650 Kg/mm^3	1400-1500 Kg/mm^3
Fire Resistance	High	High

Any good builder should be able to calculate the R and U values for you and can advise you about the relative costs of different insulation options for achieving the lowest heat loss.

Advantages and limitations for usage of thermal blocks in walls

• Provides guaranteed consistent insulation value
• Permits excess moisture to escape
• Allows easy installation of pipes, conduits, etc.
• Improves dew point
• Improves sound resistance
• Eliminates concern of shrinkage, toxic fumes or odours
• Improves the ability of blocks to resist wind driven rain.
• Can be used above or below grade

The Insulate Wall System, like conventional concrete masonry units insulated with STYROFOAM (XPS), saves job site labour costs simply because all units are delivered with insulation already in the blocks. Construction of walls is exactly like normal concrete blocks – same mortar, same manpower & same productivity. No extra glues, chemicals, fixing materials or special fixtures. In addition:

• No lost time or rework if inspection rejects the quality of on-site workmanship
• Work by other trades is performed with little danger of damage to insulation
• The block itself can be used as a bond beam or lintel eliminating the need to deliver several different types of blocks to the job site.
• The actual cost of insulation is a firm figure, as compared to estimated values used when insulation material is site installed where labour efficiency may vary and where losses may be sustained due to damage or theft

Limitations: As is the case with Dow's STYROFOAM (XPS) product, it should not be exposed to temperatures in excess of 110°F for prolonged periods of time.

Frequently Asked Questions on Thermal Blocks

1. Is it very costly?

It is a very cost effective product, due to the nature of the properties; the product is costlier than masonry hollow block. When one considers long-term benefits thermo block is value for money and one time investment and lifelong savings. A thermal block of 400X250X200 mm may cost 80 - 90 (INR) in Mumbai Region

2. What about the compressive strength?

The Thermal block has the same compressive strength of a normal 8" Hollow Blocks Thermal Blocks are very well designed to give optimum insulation as well as mechanical strength.

3. Will not STYROFOAM (XPS) catch fire easily?

Since it is enclosed on all four sides by concrete mortar joints and is sandwiched between 62.5 mm thick concrete plates, no flame due to electrical short circuiting can spread in that air tight cell. As a material, Dow STYROFOAM (XPS) is classified as B1 class building Material when tested in accordance with German DIN 4102 Standards.

4. The handling of block may be delicate?

The block is very robust and due to the high shearing strength of STYROFOAM (XPS), it is very difficult to separate the insert from the block. It requires bare minimum handling care and the blocks should not be thrown around but handled in a proper way. It can be easily handled by SRS Finlay clamps/grab units.

5. What is the life of a polystyrene insert?

STYROFOAM (XPS) will easily outlast concrete as it is not bio-degradable.

6. What about water absorption?

Since the thermal block is basically a normal concrete block, the water absorption characteristics are the same as a normal concrete block. Also STYROFOAM (XPS) has very negligible water absorption characteristics as per DIN 53428.

7. What is the effect of termites, vermin & other types of insects and is Polystyrene harmful?

Facts about STYROFOAM (EPX) Insulated Blocks

• STYROFOAM (XPS) is the best available insulation material at present for usage in walls & roofs all over the world.

• The insulation properties are very superior if the STYROFOAM (XPS) is integrated into concrete at wet stage moulding/casting to have good bonding and avoid air gaps pockets to eliminate any chance for condensation.

• Researched data proves that ‘STYROFOAM (XPS) inserted’ concrete blocks are the most cost effective in terms of Thermal insulation as against Cavity wall, clay wall, autoclaved brick wall, Cavity wall with STYROFOAM (XPS) sheet and other type of insulation.

Dow's STYROFOAM (XPS) poses no health hazards and it is immune to insects, pests, plants and micro organisms.

8. What about end blocks (at the openings. E.g. doors, windows)?

Suitable end block designs can be developed.

9. What about continuity of insulation because of mortar joints?

Thermal Insulation continuity without any thermal bridge can be made. But it should be pointed out that in other Middle East countries full mortar across the faces & sides is applied and the thermal bridge loss is very much within acceptable limits.