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How to Calculate Building Heat Loss Rate,
Insulation Values & Heating Efficiency, Calculate R, U & K Values for insulation & buildings
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The rate of un-wanted heat loss or gain in buildings or the effectiveness of any material serving as insulation can be expressed using several different measures such as R, U and K or in Europe, k-values, or as Kws (Kilowatts per square meter per hour) or in BTUs.
The best measurement of the rate at which heat is transferred through a building floor, walls, ceilings or roofs is best expressed as a U-value, as we explain here.
This article gives details and formulas for calculating R-values, U-values U-coefficient of heat loss resistance, and K-values, all ways of looking at insulation values or building heat loss rates.
Our page top photo of above-ground building perimeter & foundation insulation using styrofoam board was observed at a home Maine - Ed.
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Building Heat Loss or Gain Rate Measurements & How to Calculate & Use Them
How to measure heat transmission in materials: definition of R-values, U-values, K-values, BTU, calorie, and rates of heat loss or gain. Building design temperatures & how to use a home energy audit or heat loss analysis. What insulation "R" values should be used in a building insulation?
We also discuss how to measure or calculate heat loss in a building, defines thermal terms like BTU and calorie, provides measures of heat transmission in materials, gives desired building insulation design data, and shows how to calculate the heat loss in a building with R values or U values.
Article Contents
- DEFINITION & CALCULATION of R-VALUE
- DEFINITION & CALCULATION of K-VALUE
- DEFINITION & CALCULATION of U-VALUE
- RELATIONSHIP of R, U, & K VALUES
- RELATIONSHIP of NORTH AMERICAN RUK vs EUROPEAN kValue
- DEFINITION & CALCULATION of HEAT LOSS by EVAPORATION - e.g. from a swimming pool
- FORMULA for CALCULATING HEAT LOSS & ELECTRIC HEATER SIZE in WATTS
- FORMULAS to CALCULATE HEAT LOSS PER HOUR for a Building Using it's "R" Values or "U" Values - separate article
Definition of & How to Calculate the R value or R-coefficient of Resistance to Heat Loss in a Building or its Insulation
The "R" value of a material is defined as the material's resistance to heat flow through the material.
For purposes of insulation, you might think of "R" value as the opposite of thermal conductance, since it's described as thermal resistance or resistance to heat flow.
And you'd be correct. If thermal resistance to heat flow is "resistance" we can say that the thermal conductivity of a material is equal to the reciprocal of its thermal resistance.
More practically, by convention we use thermal resistance or R-value when buying various insulation materials.
You will almost always see an "R" value quoted for the material. In general, higher "R" means more resistance to heat loss and therefore lower heating or cooling bills for the building.
[Assuming all other factors like air leakage are either equal or have been factored into the R-value calculation.]
Mathematically, but in painfully circular reasoning, "R-value" is
simply the reciprocal of the two measures of resistance to heat flow "K-value" (R = 1/K) or "U-value" (R(whole building) = 1/U) that we define further below.
Here are Some Basic Formulas for Calculating R-Values
R-value = temperature difference [in degF] x area [sq ft] x time [in hours] / heat loss[in BTUs]
Calculate the R-Value [U.S. metrics]
R = (Heat Resistance x Degrees F x square feet) / BTUs
or stated in metric: (R-value) = t/k, measured in [editing needed]
Definition of & How to Calculate the K value or K-coefficient of heat transmission
A building's K value or K-coefficient of heat transmission is a way to express the heat loss in a building.
K Value is defined as the number of BTU's of heat moving through any material with these details:
- Per square foot of area of the material
- Per degree Fahrenheit of temperature difference
- Per inch of thickness of the material
So "K" takes a lot of variables into consideration and gives us the rate of heat loss per square foot of building surface, per inch of thickness of material in that building surface, per degree of temperature difference in Fahrenheit, in BTUs per hour.
By "degree of temperature difference in Fahrenheit" we mean that we are taking into consideration the difference in temperature on the two sides of our building surface. For example, if the indoor temperature in a building is 68 deg. F. and the outdoor temperature is 48 deg. F., then we have a 20 degree temperature difference on the two sides of the building (wall or roof for example).
This temperature difference on the two sides of a surface, say an insulated building wall, for example, is very important in understanding how a building loses heat (in the heating season) or gains heat (in the cooling season).
That's because the rate of heat transfer through a material increases exponentially as a function of the temperature difference. This is intuitively obvious and is confirmed by physicists.
For example, if the temperatures on either side of a building wall were the same, there would be no heat loss or gain through the building wall.
As the temperature difference on either side of that same wall increases, say from one degree of difference to 20 degrees of difference the rate of heat transfer increases.
An interesting version of this heat transfer theory was shared with the author in a class on how to minimize building heating costs when the instructor told us that "the thermal conductivity of finned copper heating baseboard is exponentially greater at higher temperatures".
He was saying that if we ran heating water from our heating boiler through the baseboards at 200 deg.F. we would see much more efficient heat transfer from the heating baseboards into the building.
There are other factors involved in heating system efficiency such as the length of boiler on cycle (longer is more efficient), so there was more to think about, but the instructor was applying classic heat transfer theory that is reflected in the "K" values of building insulation as we've discussed here.
Computing "K" values tells us the heat loss rate for a specific material, thickness, area, and temperature difference but while we need to be able to calculate "K" values, those alone don't tell us what's going on in an actual building.
We need to be able to combine all of the rates of heat loss (or gain) across all of the types of surfaces, insulation, and building material for the whole building - at least for all of its external or perimeter surfaces including roofs, walls, and floors as well as windows and doors. That's where the "U" value makes its appearance.
Definition of & How to Calculate the U value or U-coefficient of heat loss resistance
A building's "U" value can be defined as the rate of unwanted heat loss or gain of an entire building.
A building's "U" value or U-coefficient of resistance of heat loss is a related measure of resistance to thermal energy or heat flow out of a building (if it's warmer inside than outside) or conversely the same concept works in a warm climate where air conditioning is in use, except that we expect outside heat to be flowing into the building.
Why do we need to compute the "U" value for a building, wall, ceiling, floor or other material? The "U" value is the most broad or comprehensive view of a building's heat loss or gain rate.
Computing "K" values alone tells us the heat loss rate for a specific material, thickness, area, and temperature difference but while we need to be able to calculate "K" values, those alone don't tell us what's going on in an actual building.
To calculate the "U" value, or overall heat loss (or gain if we're air conditioning) for a building, we need to add the "R" values for each material in the structure, and to factor in the total area of each material in the structure.
We discuss this procedure in more detail below at "Calculating Heat Loss for a Building".
We need to be able to combine all of the rates of heat loss (or gain) across all of the types of surfaces, insulation, and building material for the whole building - at least for all of its external or perimeter surfaces including roofs, walls, and floors as well as windows and doors. That's where the "U" value makes its appearance.
A building's "U" value or U-coefficient of resistance of heat loss is a related measure of resistance to thermal energy or heat flow out of a building (if it's warmer inside than outside) or conversely the same concept works in a warm climate where air conditioning is in use, except that we expect outside heat to be flowing into the building.
A building's "U" value is much more complete, and therefore useful than "K" values alone because a building's "U" value combines the "K" factors for all of the building's surfaces and materials.
In other words, we add the effects of heat loss (or gain), still expressed in the number of BTU's per hour per square foot of area, and still expressed per degree of Fahrenheit of temperature difference and still expressed per inch of thickness of material (just as with "K" values), for all of the substantial areas and surfaces of the exterior of a building's floors, walls, windows, doors, ceilings, or roofs (if cathedral ceilings are present).
U-value = BTUs / (hours x Degrees F x Square Feet)
A building's "U" value is much more complete, and therefore useful than "K" values alone because a building's "U" value combines the "K" factors for all of the building's surfaces and materials.
In other words, we add the effects of heat loss (or gain), still expressed in the number of BTU's per hour per square foot of area, and still expressed per degree of Fahrenheit of temperature difference and still expressed per inch of thickness of material (just as with "K" values), for all of the substantial areas and surfaces of the exterior of a building's floors, walls, windows, doors, ceilings, or roofs (if cathedral ceilings are present).
To calculate the "U" value, or overall heat loss (or gain if we're air conditioning) for a building, we need to add the "R" values for each material in the structure, and to factor in the total area of each material in the structure. We discuss this procedure in more detail below at "Calculating Heat Loss for a Building".
Relationship of R, U, and K Values
What do U and K values have to do with R-values?
As you'll read below "K" measures the heat flow through an individual substance and "U" as most folks use it measures the overall building heat loss by adding all of the various areas and substances together.
U-values measure the thermal transmittance of heat in or out of a building and combines heat movement by all principles that are occurring at a building: radiation, convection, and conduction.
So you can see that "U" values are more complex but really more complete than "R" values.
How to Escape the Circular Reasoning of R=1/K
We can escape the horrible circular reasoning that appears in some writing about heat loss measurements if any one of the three values, R, U, K is defined independently.
We'll take a stab at this just below.
The R-value of a material is typically expressed as R [resistance to heat flow] per inch of material thickness. More technically, "R-value" is measured in mete Watt [metric system] or h/Btu [U.S. measurement system].
Materials may be rated in R per inch or R per meter or similar measures.
Sort out the Definitions of U.S. k-values, lambda or values, and European k-values
Note: In the U.S. k-value when discussing the heat loss resistance of window glazing is equivalent to lambda value in Europe, and in case that's not confusing enough, an older European k-value (the total insulation value of a building) is currently referred to in Europe as U-value.
You'll recall from our notes above that U-value is a reciprocal or 1/R-value. - Wikipedia web search 03/11/2011 see "Thermal Conductivity".
To convert U.S. R-values to European U-values:
[ (1 / R-value USA) x 0.176 ] / 1 = U Europe
and
U Europe = [watts / kelvin x meters2]
Beginning at HEAT LOSS in BUILDINGS article series explains how to insulate a building and how much insulation is needed including how to measure or calculate heat loss in a building, defines thermal terms like BTU and calorie, provides measures of heat transmission in materials, gives desired building insulation design data, and shows how to calculate the heat loss in a building with R values or U values
Formula-R™ and Owens Corning™ which may be visible in this photograph of pink Styrofoam™ insulation boards are registered trademarks of Owens Corning® and were photographed at a Home Depot® building supply center.
How to Calculate Heat Loss & Electric Heater Size in Watts
For a typical building we compute the total building surface area, adding the area in square meters of the roof surfaces, wall surfaces and floor surfaces. Then using simple constants for typical building roofs, floors and walls we calculate the total surface area heat loss.
Watch Out: this is a simplifed example making quite a few assumptions. Your building's heat loss rate may vary significantly depending on your local climate, outdoor weather, wind, and building insulation and infiltration losses.
We add a factor for estimated rate of heat loss through air leaks or deliberate building outdoor ventilation.
Finally, expressing the heat loss in watts we can calculate the necessary electric heater size by multiplying the heat loss rate in Watts times the desired temperature "lift" in degrees.
This example is from Tombling cited below.
Example heat loss calculation
This example, by Tomblilng, assumes a simple building with the following dimensions, U-values, and design temperatures
Building Dimensions in Meters
- Length = 30 meters (m)
- Width = 10 m
- Eave height = 2 m
- Ridge height = 3 m
Building U Values (Watts/M2 deg.C)
- Uvalue - Walls = 2.6
- Uvalue - Roof (corrugated asbestos sheeting) = 5.7
- Uvalue - Floor (concrete slab) = 0.7
Building Design Temperature
- Minimum Aambient outdoor temperature (Centigrade) = -5 C
- Required indoor temperature = 20 C
Surface Heat Loss Calculation
- Temperature lift = 20 - (-5) = 25 deg. C
- Area of roof = 2 x 5.09 x 30 = 305.4 m2
- Area of walls = (2x2x30) + 10(2+3) = 180 m2
- Area of floor = 30 x 10 = 300 m2
- Heat loss through roof = 305.4 x 5.7 = 1740 W
- Heat loss through walls = 180 x 2.6 = 468 W
- Heat loss through floor = 300 x 0.7 = 210 W
- Total surface heat loss = 2418 W
Assuming 20% for heat loss through ventilation
- Total heat loss = 1.2 x 2418 = 2901 W
Heater size required = total heat loss x temperature lift = 2901 x 25 = 72525 W
In this example 4 - 20kW Activair Ace electric fan heaters , 5 - 15kW Activair portable heaters or 4- 21kW Activair wall mounted electric heaters are needed.
References
- Tombling, PERFORMING HEAT LOSS CALCULATIONS on a STRUCTURE [PDF] to calculate required size of electric heater needed, (2003) ActivAir, Tombling, W. Tombling Ltd. Wembley House Dozens Bank West Pinchbeck Spalding Lincolnshire PE11 3ND U.K., Web: https://www.tombling.com/ - retrieved 2022/12/24, original source: https://www.tombling.com/heaters/heatloss.htm
- Watlow, HOW MUCH HEAT DO YOU NEED? CALCULTIONS for HEAT ENERGY [PDF] (2020) Watlow, US: Watlow Energy Processes
6410 Langfield Road
Building G
Houston TX 77092
Energy Processes, Tel: 1-800-928-5692, Web: watlow.com
Canada: (Ontario distributor) Bluewater Heater 2220 Olympia Dr Unit 1 Oldcastle Ontario N0R 1L0 Ontario All 519 737-7333 519 737-7337 email us www.bluewaterheater.com - note that the company has offices in other provinces, see https://www.watlow.com/Contact-Us/sales-office-locator
Australia, Watlow Energy Processes 1800 870 850
New Zealand, Homersham Ltd 3E Homersham Place, Burnside Christchurch New Zealand All +64 3358 8309 +64 3 358 2516
Europe (offices in most countries) Watlow United Kingdom Robey Close, Linby Ind. Estate Linby Nottingham NG15 8AA United Kingdom All +44 115 964 0777 - retrieved 202212/24, original source: https://www.watlow.com/Tools/DownloadBlogPost.aspx?bid=440467EC2F9E4B999464800EE7D94904
Excerpt: Most electrical heating problems can be readily solved by determining the heat required to do the job. The heat requirement must be converted to electrical power and the most practical heater can then be selected for the job. Whether the problem is heating solids, liquids or gases, the method, or approach, to determining the power requirement is the same.
Formulas Used to Calculate the Rate of Building Heat Loss Per Hour for a Building Using it's "R" Values or "U" Values
Formulas and an explanation of how we use R U or K values to determine the rate of heat loss at a building (or heat gain if we are cooling it) are
at HEAT LOSS in BUILDINGS or within that article
at section Formulas to Calculate the Rate of Heat Loss Per Hour for a Building Using it's "R" Values or "U" Values.
Also see additional research citations at the page bottom REFERENCES section.
Formula for Evaporation As a Factor in Heat Loss
Useful in understanding heat loss at swimming pools or solar ponds is the formula for evaporation losses, given just below.
Pevaporationa = (25+19Vw) x S x (X - X') x LvA x t/1000c
Where:
- Pevapo = evaporation losses (kWh)
- (25 + 19Vw) = empirical formula giving the ratio of the heat exchange coefficient hconv by convection between the water and air (W / mA²K) on the Cair specific heat of air (= 0,277Wh / kg of air.K)
- Vw = wind speed across the surface of the pond or pool in (meters / second)
- S = the pool surface aerea in square meters (mA²)
- X = specific humidity of saturated air at the temperature of the water (grams of water / kilogram air)
- X ' = specific humidity of ambient air at the temperature of the water (g water / kg air)
- Lv = enthalpy (or latent heat) of vaporization of water: 0.625 Wh / g
- t = time without solar pool or pond cover (in hours)
In some expert sources that we reviewed we read that in general, evaporation from a pool or pond surface explains about 30% to one half of the total heat loss.
Surface evaoration in summer will remove about 50 mm of water in seven days. In energy this is about 150 Kwh or Kilowatt hours. Higher wind velocity and location in a dry climate such as Arizona will increase the evaoration rate significantly. Use of a pool cover will significantly reduce both evaporation loss of water and heat.
References
- Research Gate, "How do I calculate heat loss by evaporation from the surface of an active swimming pool" - retrieved 2022/12/24, original source: https://www.researchgate.net/post/How_do_I_calculate_heat_loss_by_evaporation_from_the_surface_of_an_active_swimming_pool
- Schaefer, Skip, HOW to CALCULATE HEAT LOSS [PDF] - Industrial heating Systems Co., 9530 W Bethel Ct Ste B, Boise, ID 83709 USA, Web: https://industrialheatingsystems.com/ Tel: 208-323-6143 - retrieved 2022/12/24 original source: https://industrialheatingsystems.com/How-calculate-heat-loss.html
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Continue reading at INSULATION R-VALUES & PROPERTIES - R-values & U Values of various materials, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.
Or see these
Recommended Articles
- ENERGY SAVINGS in BUILDINGS - home
- ENERGY USE MONITORING, SOLAR
- HEAT LOSS INDICATORS - where is the building losing heat during the heating season, or gaining unwanted heat during the cooling season
- HEAT LOSS R, U & K VALUE CALCULATION - heat loss (or gain) rates for buildings, insulation, or other materials
- INSULATION INSPECTION & IMPROVEMENT - home
- INSULATION R-VALUES & PROPERTIES - R-values & U Values of various materials
- PERM RATINGS of BUILDING MATERIALS
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HEAT LOSS R U & K VALUE CALCULATION at InspectApedia.com - on-line encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.
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INDEX to RELATED ARTICLES: ARTICLE INDEX to BUILDING ENERGY SAVINGS
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Citations & References
In addition to any citations in the article above, a full list is available on request.
- Thanks to Sanjiv Malkan for correcting our formula for R-values 3/22/2009.
- Thanks to Steven Muscato for correcting our formula for U-Values 7/31/2009
- Alzetto, Florent, Guillaume Pandraud, Richard Fitton, Ingo Heusler, and Herbert Sinnesbichler. QUB: A fast dynamic method for in-situ measurement of the whole building heat loss [PDF] Energy and Buildings  174 (2018): 124-133.
Abstract
QUB is an innovative method enabling the experimental measurement of the total heat loss coefficient (HLC) of a building envelope in one night only. It is based on a simple theory, yet can be demonstrated to be accurate even in a short time and in real buildings, as long as certain experimental conditions are fulfilled.
This study combines analytical and numerical approaches to exactly solve the temperature response of an equivalent building submitted to a QUB test. This allows understanding that even with a short time experiment (less than a night), a reasonable accuracy on the estimated HLC can be obtained.
The experiment has to be designed following a simple heating power criterion. Calculation is then tested experimentally in various cases whether in climate chamber or in real field, and whether on light weight/not insulated building or a heavy weight/highly insulated building.
Results show that the QUB method performed by fulfilling this criterion is a promising method to estimate the HLC of a real building in the field with a reasonable accuracy in one night. - ASHRAE resources on building insulation, dew point and wall condensation - see the ASHRAE Fundamentals Handbook, available in many libraries.
- 2005 ASHRAE Handbook : Fundamentals: Inch-Pound Edition (2005 ASHRAE HANDBOOK : Fundamentals : I-P Edition) (Hardcover), Thomas H. Kuehn (Contributor), R. J. Couvillion (Contributor), John W. Coleman (Contributor), Narasipur Suryanarayana (Contributor), Zahid Ayub (Contributor), Robert Parsons (Author), ISBN-10: 1931862702 or ISBN-13: 978-1931862707
- 2004 ASHRAE Handbook : Heating, Ventilating, and Air-Conditioning: Systems and Equipment : Inch-Pound Edition (2004 ASHRAE Handbook : HVAC Systems and Equipment : I-P Edition) (Hardcover)
by American Society of Heating, ISBN-10: 1931862478 or ISBN-13: 978-1931862479
"2004 ASHRAE Handbook - HVAC Systems and Equipment The 2004 ASHRAE HandbookHVAC Systems and Equipment discusses various common systems and the equipment (components or assemblies) that comprise them, and describes features and differences.
This information helps system designers and operators in selecting and using equipment. Major sections include Air-Conditioning and Heating Systems (chapters on system analysis and selection, air distribution, in-room terminal systems, centralized and decentralized systems, heat pumps, panel heating and cooling, cogeneration and engine-driven systems, heat recovery, steam and hydronic systems, district systems, small forced-air systems, infrared radiant heating, and water heating);
Air-Handling Equipment (chapters on duct construction, air distribution, fans, coils, evaporative air-coolers, humidifiers, mechanical and desiccant dehumidification, air cleaners, industrial gas cleaning and air pollution control); Heating Equipment (chapters on automatic fuel-burning equipment, boilers, furnaces, in-space heaters, chimneys and flue vent systems, unit heaters, makeup air units, radiators, and solar equipment);
General Components (chapters on compressors, condensers, cooling towers, liquid coolers, liquid-chilling systems, centrifugal pumps, motors and drives, pipes and fittings, valves, heat exchangers, and energy recovery equipment); and Unitary Equipment (chapters on air conditioners and heat pumps, room air conditioners and packaged terminal equipment, and a new chapter on mechanical dehumidifiers and heat pipes)." - 1996 Ashrae Handbook Heating, Ventilating, and Air-Conditioning Systems and Equipment: Inch-Pound Edition (Hardcover), ISBN-10: 1883413346 or ISBN-13: 978-1883413347 ,
"The 1996 HVAC Systems and Equipment Handbook is the result of ASHRAE's continuing effort to update, expand and reorganize the Handbook Series. Over a third of the book has been revised and augmented with new chapters on hydronic heating and cooling systems design; fans; unit ventilator; unit heaters; and makeup air units.
Extensive changes have been added to chapters on panel heating and cooling; cogeneration systems and engine and turbine drives; applied heat pump and heat recovery systems; humidifiers; desiccant dehumidification and pressure drying equipment, air-heating coils; chimney, gas vent, fireplace systems; cooling towers; centrifugal pumps; and air-to-air energy recovery. Separate I-P and SI editions." - Principles of Heating, Ventilating, And Air Conditioning: A textbook with Design Data Based on 2005 AShrae Handbook - Fundamentals (Hardcover), Harry J., Jr. Sauer (Author), Ronald H. Howell, ISBN-10: 1931862923 or ISBN-13: 978-1931862929
- 1993 ASHRAE Handbook Fundamentals (Hardcover), ISBN-10: 0910110964 or ISBN-13: 978-091011096
- Burman, Esfand, Dejan Mumovic,Judit Kimpian, Towards measurement and verification of energy performance under the framework of the European directive for energy performance of buildings [PDF] Energy, 77 (2014) pp. 153-163
Abstract:
Directive 2002/91/EC of the European Parliament and Council on the Energy Performance of Buildings has led to major developments in energy policies followed by the EU Member States.
The national energy performance targets for the built environment are mostly rooted in the Building Regulations that are shaped by this Directive. Article 3 of this Directive requires a methodology to calculate energy performance of buildings under standardised operating conditions.
Overwhelming evidence suggests that actual energy performance is often significantly higher than this standardised and theoretical performance. The risk is national energy saving targets may not be achieved in practice.
The UK evidence for the education and office sectors is presented in this paper. A measurement and verification plan isproposed to compare actual energy performance of a building with its theoretical performance using calibrated thermal modelling. Consequently, the intended vs. actual energy performance can be established under identical operating conditions.
This can help identify the shortcomings of construction process and building procurement. Once energy performance gap is determined with reasonable accuracy and root causes identified, effective measures could be adopted to remedy or offset this gap. - Claesson, Johan, and Carl-Eric Hagentoft. "Heat loss to the ground from a building. General theory." Building and Environment 26, no. 2 (1991): 195-208.
Abstract
The heat flow to the ground from a building depends on the complicated thermal process in the ground. An extensive analysis of the processes involved is presented in this series of papers. A main goal is to obtain sufficiently accurate, and as simple as possible, formulae for the heat flow to be used for design purposes.
This first papers presents the general theory that is used. The main difficulties in obtaining manageable formulae concern the three-dimensionality of the thermal problem, the strong temporal variability of the outdoor temperature, and the large number of parameters involved in describing foundation geometry, thermal insulation and so on.
Superposition and dimensional analysis are used to meet these difficulties. Basic components of the thermal process are the steady-state solution, the solutions for a periodic outdoor temperature and a unit step of the outdoor temperature.
The dimensional analysis leads to a steady-state heat loss factor, corresponding factors for the periodic solution and the temperature step. The penetration range of the two transient processes is studied in detail. It is shown that these normally involve only a region around the periphery. So-called edge solutions, which are two-dimensional and depend on the parameters near the periphery only, may be used. - Hamburg, Anti, Alo Mikola, Tuule-Mall Parts, and Targo Kalamees. "Heat Loss Due to Domestic Hot Water Pipes." Energies 14, no. 20 (2021): 6446.
Abstract
Domestic hot water (DHW) system energy losses are an important part of energy consumption in newly built or in reconstructed apartment buildings. To reach nZEB or low energy building targets (renovation cases) we should take these losses into account during the design phase.
These losses depend on room and water temperature, insulation and length of pipes and water circulation strategy. The target of our study is to develop a method which can be used in the early stages of design in primary energy calculations. We are also interested in how much of these losses cannot be utilised as internal heat gain and how much heat loss depends on the level of energy performance of the building.
We used detailed DHW system heat loss measurements and simulations from an nZEB apartment building and annual heat loss data from a total of 22 apartment buildings. Our study showed that EN 15316-3 standard equations for pipe length give more than a twice the pipe length in basements.
We recommend that for pipe length calculation in basements, a calculation based on the building's gross area should be used and for pipe length in vertical shafts, a building's heating area-based calculation should be used. Our study also showed that up to 33% of pipe heat losses can be utilised as internal heat gain in energy renovated apartment buildings but in unheated basements this figure drops to 30% and in shafts rises to 40% for an average loss (thermal pipe insulation thickness 40 mm) of 10.8 W/m and 5.1 W/m.
Unutilised delivered energy loss from DHW systems in smaller apartment buildings can be up to 12.1 kWh/(m2A·a) and in bigger apartment buildings not less than 5.5 kWh/(m2A·a) (40 mm thermal pipe insulation).
Keywords: DHW heat loss; DHW circulation; energy performance Insulate & Weatherize (Taunton's Build Like a Pro), Bruce Harley. R - US DOE INSULATION: ADDING INSULATION TO AN EXISTING HOME [PDF] U.S. Department of Energy - tips on how to do your own check for the presence of absence of insulation in a home
- Insulation Types, table of common building insulation properties from U.S. DOE. Readers should see INSULATION R-VALUES & PROPERTIES our own table of insulation properties that includes links to articles describing each insulation material in more detail.
- The National Institute of Standards and Technology, NIST (nee National Bureau of Standards NBS) is a US government agency - see www.nist.gov
- "A Parametric Study of Wall Moisture Contents Using a Revised Variable Indoor Relative Humidity Version of the "Moist" Transient Heat and Moisture Transfer Model [copy on file as/interiors/MOIST_Model_NIST_b95074.pdf ] - ", George Tsongas, Doug Burch, Carolyn Roos, Malcom Cunningham; this paper describes software and the prediction of wall moisture contents. - PDF Document from NIS li class="LI_Spaced">Oliveti,G, N. ArcuriD. MazzeoM. De Simone A new parameter for the dynamic analysis of building walls using the harmonic method [PDF] (2013) International Journal of Thermal Sciences, No 88 (2015) 96-109
- Principles of Heating, Ventilating, And Air Conditioning: A textbook with Design Data Based on 2005 ASHRAE Handbook - Fundamentals, Harry J., Jr. Sauer, Ronald H. Howell, William J. Coad. Quoting
... textbook for college level HVAC courses or independent study and review, especially when combined with the 1997 ASHRAE Fundamentals Handbook. Contains the most current ASHRAE procedures and definitive, yet easy to understand, treatment of building HVAC systems -- from basic principles through design and operation. Dual units of measurement. - Super-Insulated Retrofit Book: A Homeowner's Guide to Energy-Efficient Renovation, Robert Argue
- The super-insulated retrofit book: A homeowner's guide to energy-efficient renovation (Sun builders series), Brian Marshall
- Understanding Ventilation: How to Design, Select, and Install Residential Ventilation Systems, John Bower, Quoting:
Understanding Ventilation is the only book that covers all aspects of exchanging the air in houses: infiltration, equipment selection, design, heat-recovery ventilators, sizing, costs, controls, whole-house filters, distribution, and possible problems that a ventilation system can cause--all in easy-to-understand language. - In addition to citations & references found in this article, see the research citations given at the end of the related articles found at our suggested
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Abstract:
The authors propose a methodology to schematize correctly the capacitive effects in the transmission of heat in the multilayered walls of buildings. An analytical study is presented related to a steady periodic regime allowing consideration of three external loads acting singularly or simultaneously: air temperature, apparent sky temperature and incident solar irradiation. Such a study is applied in the case of four traditional types of wall (A e brick wall, B e hollow wall, C e polarized brick wall, D e prefabricated wall).
The expression of the oscillating heat flux, which penetrates the internal environment, and the conductive heat flux which penetrates the wall in contact with the external air, was obtained by means of the electrical analogy and the resolution of the equivalent circuit.
It is demonstrated that the nondimensional periodic global transmittance, the ratio between the heat flux which is transferred to the indoor environment and the external heat flux, with the plant turned on, is the most suitable nondi- mensional parameter for the dynamic analysis of the walls. This parameter allows for the evaluation of all the typical dynamic quantities for the complete description of the thermal behavior of the walls.
- Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: info@carsondunlop.com. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The HOME REFERENCE BOOK - the Encyclopedia of Homes and to use illustrations from The ILLUSTRATED HOME .
Carson Dunlop Associates provides extensive home inspection education and report writing material. In gratitude we provide links to tsome Carson Dunlop Associates products and services.
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