2. “There is a tree
here, there is one
there and a third
one there.
I do not want to
cut the trees and
this principle has
much to
do with the shape
of a house”
3. What is inside???
A look
around the
globe
Definition
Terms
related to
thermal
insulation
Factors
related with
thermal
insulation
Insulating
materials
Miscellaneou
s
How to
insulate?
5. • Process of insulating a material
from transferring heat to another
material or surroundings
• Aim is to retain heat within the
interior during winter and
dissipate heat during summer
7. • Polar bear has a thick fur to
protect itself from the chilling
environment
• Eskimos use this fabrics to
stay warm
IN THE NATURE
8. Snow and ice work
as insulators to trap
body heat inside
the igloo..
Thus, the
occupants of an
igloo double as
9. Building dates back to Neolithic
age
Thick stones as good insulators
Green roofing to reduce the
heat emission
Circular shape to reduce
surface area exposed to
atmosphere, to reduce heat
loss
Skara Brae Village, Scotland
11. Form of heat transfer
that occurs between
two separated bodies
as a result of
electromagnetic
radiation
Form of heat transfer
through a body that occurs
without any movement of
body; result of molecular
or electron action
Form of heat transfer that
results from gross movement
of liquids or gases
Ref: “Air conditioning principles and systems: an energy approach” by Edward.G.Pita
12. Absorptivity (a): Ratio of radiation
absorbed by the surface compared
an absorbing black body under the
same conditions.
Reflectivity (r): Ratio of reflected heat
to that of the total incident on a
surface at a certain mean
Emissivity (e): Ratio of heat emitted
by a surface as compared to that of
absolutely black surface, under
conditions.
13. Conductance (C): Heat flow rate through a unit area of body when the
temperature difference between the two surfaces is 1◦C (W/m²◦C)
Resistance (R): Measure of resistance of a material to heat flow. Also the
reciprocal of conductance. (m²◦C/W)
𝑅 = 𝑏
,
𝑘
b = thickness of the material in metres,
k = Conductivity of the material
Air-to-air Resistance (Ra):It is the measure of total resistance of the body,
including the resistance of thin layers of air on both sides of the material.
1 1
1
𝑓𝑖
𝑅𝑎 =
𝑓𝑖
+ 𝑅 +
𝑓𝑜
= Internal surface resistance of air;
1
𝑓𝑜
= External surface resistance of air
Thermal Transmittance (U – Value): Measure of heat transmittance of a
material. Quantified as reciprocal of Ra.
15. THEORY OF HEAT TRANSMISSION
• Rate of heat transfer depends on the thermal conductivity of material
• Low conductivity when the solid matter present is less
• Moisture can increase the conductivity by 0.6059W/mK at 20◦C
• Water, though have less conductivity value, can carry heat through
convection
• Conductivity of building materials vary depending on Bulk dry density and
Moisture content
• In gases, heat is transmitted through convection and radiation
Ref: “Thermal and acoustic insulation”, R.M.E.Diamant, P-4
16. CONDUCTION
• Amount of heat transferred proportional to the
difference in temperature
• Increases with the area of contact and
decreases with the perpendicular distance.
• Varies significantly with materials
• More in metals and lowest in organic foams
• Within a material, depends on bulk dry
density and moisture content
• Prominent in solids, moderately in liquids,
and least in gas
Ref: “Thermal and acoustic insulation” by R.M.E. Diamant. P-26
18. CONVECTION
• Fluid gets warmed up by contact with a
surface and moves away, carrying the heat
with it
• Could be “Forced” convection or “Free”
convection
• Part of fluid in touch with hot surface gets
warmed up, change density and moves away.
• Prominent in liquids and gases
Ref: SP41 – P 35
19. RADIATION
• Radiation can occur across vacuum
• Heat transfer is by electromagnetic
radiation
• When they travel at speed of light,
particles have a certain mass. When this
is stopped, Kinetic energy gets converted
into heat
• At night, heat radiates back to
atmosphere
• Prominent in solids, liquids and gases
Ref: SP41 – P 36
20. PROBLEMS IN EVALUATING INSULATION
PROPERTIES
• Walls, roofs, floors and windows are composite materials and their nature can vary
diurnally
• Influence of ventilation is prominent and cannot be measured easily
• Internal temperature differs from space to space and also during various hours of the
day
• During daytime, solar radiation is high and external surfaces will have a higher
temperature than ambient temperature, called “Sol-air Temperature”. At night surface
temperature will be less than surroundings due to “Radiation cooling”
Ref: “Thermal and acoustic insulation” by R.M.E. Diamant. P-28
22. PERIODIC HEAT FLOW
• Diurnal variation in temperature
produce an approximate 24hour cycle
of increasing and decreasing
temperature
• Heat absorbed during radiation is
emitted after sometime
• Time lag is the difference in time
between peaks of outside and interior
temperature peaks
• More the specific heat of material,
more will be the time lag
• Decrement factor = Ti(max) / To(max)
Ref: “Manual of tropical housing and building” by O.H.Koenigsberger, P-84
25. In two or three columns
Outside
✘ Used where walls have no
internal cavity
✘ No need to disturb the
existing walls or internal
decorations
✘ More densified or specific
heat capacity materials
✘ Water repellent and UV-
resistant
Sandwiched
✘ Widely used
✘ Used during construction of
wall itself
✘ Compressive or tensile
strength is not a criteria
✘ Protected from UV and
chemical attacks
Inside
✘ Room heats up quickly
✘ Low specific heat capacity
materials
✘ Must be resistant to
accidental knocks and
vapours
Position Time lag (hours) Decrement factor
Under the roof slab 3 0.450
Over the roof slab 11.5 0.046
Ref: “Thermal and acoustic insulation” by R.M.E. Diamant. P-51
26. HEAT TRANSFER IN WINDOW
• Appreciable heat transfer by
radiation
• Permits 86-88% radiation
• Can be insulated by multiple
glazing, using tinted or
patterned glasses or by using
curtain or venetian blinds
30. Aluminium Foil
• Reflects 98% of the radiation
• High conductivity of 235W/mK
• Used in elements having
cavity insulation
• Not suitable if convection is
large
• Used in walls and roofs
• Panels are used when
flexibility is not required
Ref: “Thermal and acoustic insulation” by R.M.E. Diamant.
31. Reflective Vinyl Film (Reflectafoil)
• Thin film of about 100
microns thickness
• 99% reflectivity
• Do not get oxidised like
Aluminium
• Cheaper per units area
• Very low structural strength
• Impregnated on boards to
make rigid, if required
Ref: “Thermal and acoustic insulation” by R.M.E. Diamant.
32. GYPSUM
A) INSULATING WALL
BOARDS
• Internal core of aerated
gypsum plaster which neither
expands nor contracts
• Surfaced with mill boarding on
both sides and covered on
one side with aluminium foil
• Conductivity is 0.16W/mK
B) GYPSUM CEILING PANELS
• Used as suspended ceilings
• Good acoustic insulator
• Insulation can be increased by
filling air gap with other
insulating materials like wool
C) IMPREGNATED
WOOD WOOL SLABS
• Made by pressing
wooden fibres and
impregnating under
pressure with gypsum
• Conducitvity of
0.085W/mk
Ref: “Thermal and acoustic insulation” by R.M.E. Diamant.
33. FOAM GLASS
• Opaque glass material
• Compressive strength of about
10MPa
• Innumerable interconnecting air
cavities
• Made from borosilicate glasses.
• Used in walls, floors, and roofs
• Conductivity of 0.055W/mK at 20◦C
Ref: “Thermal and acoustic insulation” by R.M.E. Diamant.
34. GLASS FIBRE WOOL
• Soda glass heated with
CaCO3, SiO2 and Na2CO3
• CO2 evolved is trapped to
cause air cavities
• Conductivity of 0.039W/mK
• Used widely as acoustic
insulators also
• Used in walls and roofs
Ref: “Thermal and acoustic insulation” by R.M.E. Diamant.
35. ROCK WOOL / MINERAL WOOL
• Made from diabase, a volcanic rock
• Crushed and melted with coke and lime
and cooled rapidly to room temperature
• High fire resistance
• Do not absorb moisture
• Used as boards and batts
Ref: “Thermal and acoustic insulation” by R.M.E. Diamant.
36. VERMICULITE
• Replacement for asbestos
• Used mainly in attic insulation
• Made of aluminium-iron magnesium
silicates
• Conductivity of 0.062W/mK
• Holds moisture
Ref: “Thermal and acoustic insulation” by R.M.E. Diamant.
37. POLYURETHANE FOAMS
• Polymer material
• Contains non-interconnected closed
cells filled with fluorohydrocarbon
gases
• Volume expands to about 30-35
times
• Can be sprayed directly to walls
• Highly adhesive
Ref: “Thermal and acoustic insulation” by R.M.E. Diamant.
38. EXPANDED POLYSTYRENE
• Made from polystyrene polymer
• Act as both thermal and acoustic
insulation
• EPS beads can be blown into wall
cavities
• Very low water absorption, in the
range of 2-3%
• Not fire resistant. Softens at 75◦C
Ref: “Thermal and acoustic insulation” by R.M.E. Diamant.
39. 6
Insulation Mechanisms
Slab or block insulation, blanket insulation, loose fill insulation, batt insulation, spray foam
insulation, reflective sheet insulation and board insulation
40. SLAB / BLOCK INSULATION
• Thermal insulation which is fabricated
in rigid or semirigid form
• Designated if face dimensions are less
and thickness greater than a board
• These may be made of cork, mineral
wool, vermiculite, asbestos etc.
• Fixed to walls, slabs and floors
Ref: “Thermal and acoustic insulation” by R.M.E. Diamant.
41. BLANKET INSULATION
• Comes in rolls, with or without
facing
• Cut as per the required dimensions
and placed
• Flexible and fibrous
• Made from mineral wool, glass
wool, wood wool etc.
• Mostly used in walls and roofs
Ref: “Thermal and acoustic insulation” by R.M.E. Diamant.
42. LOOSE FILL INSULATION
• Either produced as or broken
down into shreds
• Poured or blown into the
concerned area
• Air cavities play a major role
• Vermiculite, EPS beads, cellulose,
fibreglass etc. can be used
Ref: “Thermal and acoustic insulation” by R.M.E. Diamant.
43. BATT INSULATION
• Similar to blanket insulation
• Less width and more thickness
• Stored as rolls and cut to
required shape
• Used to insulate walls and roof
• Made of rock wool, glass wool,
wood wool etc.
Ref: “Thermal and acoustic insulation” by R.M.E. Diamant.
44. INSULATION BOARDS
• Made of impregnating fibre type
insulators with resins or
vegetable pulp
• Can be used as structural or
finishing material
• Used as partition walls also
• Installed in walls, roofs and floors
Ref: “Thermal and acoustic insulation” by R.M.E. Diamant.
45. INSULATION USING REFLECTIVE SHEETS
• High reflectivity and low emissivity
• Preferred in exteriors as conductivity
is more
• Used as sheets or panels
• Used for insulating roofs and exterior
walls
Ref: “Thermal and acoustic insulation” by R.M.E. Diamant.
46. SPRAY FOAM INSULATION
• Materials are made to expand by
adding air
• Sprayed through nozzles to the
concerned area
• Large number of closed or unclosed
cavities
• Usually used in attics and walls, in
the interior
• Polyurethane, EPS etc. are used
Ref: “Thermal and acoustic insulation” by R.M.E. Diamant.
48. SOL-AIR TEMPERATURE
• Temperature which combines the effect of radiation incident on a building with the
effect of warm air
• Defined as “ the outside temperature, which in the absence of solar radiation,
would give the same temperature distribution and rate of heat transfer, as the
environment in question”
Ts = To + (I x a)/fo
• Significant in the periodic heat flow measurement, where the surface temperature
would be well above the ambient air temperature
Ref: “Thermal and acoustic insulation” by R.M.E. Diamant.
49. CONDENSATION
• If warm air, capable of holding a certain amount of moisture, hits a cool surface, it is
also cooled.
• When the air is cooled, ability to carry moisture decreases and drips of water at the
surface
• If the wall is porous enough for the vapour to reach the inside insulator, insulator
gets dampened and its function reduces
• Adequate ventilation is to be ensured to prevent condensation
Ref: “Thermal and acoustic insulation” by R.M.E. Diamant.
