Presentation on theme: "Wall Insulation and Whole Building Energy Performance John Swink, PE, LEED-AP Acme Brick Company 817-714-9523."— Presentation transcript:
Wall Insulation and Whole Building Energy Performance John Swink, PE, LEED-AP Acme Brick Company
Avoid disinformation about saving energy in buildings. Understand real thermal performance of wall systems Demystify whole building energy analysis. Wall Insulation and Whole Building Energy Performance
Learning Objectives 1.Learn the TRUE U and R values of many common wall systems. 2.Learn how to calculate true U and R values for complex building envelope components. 3.Learn how eQuest and Simergy can help you design high performance buildings to meet sustainable goals. 4.Learn to integrate economical building envelopes with high performance mechanical systems for the most cost-effective energy performance.
1. True U and R Values in Building Walls Introduction – The LEED® Mandate Rising energy costs and concern for the environment have led many groups, including AIA, ASHRAE, USGBC and ICC to support much higher expectations for building energy performance. There have been many predictions and endeavors to build zero-energy and near-zero energy buildings. But there are practical limits on building performance. Today we will look at the entire building envelope to optimize the wall systems, including opaque and glazed areas, to see what those limits are, and how best to design buildings for optimum performance and value.
Introduction – The LEED® Mandate Traditionally, heating and cooling of buildings has been the purview of mechanical engineers on the design team. But choices made by architects and structural engineers have a significant impact on the energy performance of our buildings. So we need to understand as fully as possible how those choices can help or hurt the building’s overall energy performance. Today we will investigate the impact of various types of building envelope construction on the performance of those buildings. 1. True U and R Values in Building Walls
Introduction – The LEED® Mandate – ever-decreasing energy demand for buildings. 1.We examine popular wall systems for ACTUAL heat flow a.All include air and moisture barriers b.Alternates for glazing area considered. c.Mass not included in calculations, but will benefit 2.eQUEST or Simergy lets you quickly study the effects of different wall systems on whole building energy performance. Occupancy types are critical for effective evaluation of building performance. Energy demands vary widely:
Session Outline 1.Dispel some popular myths about R values 2.Compare popular wall systems 3.Detailed look at wall system heat flow 4.ORNL study of mass walls in a model house 5.Proposed mass house for optimum energy performance 6.School energy performance study at University of Louisville
Those “R” Lies “Oh, what a tangle web we weave when first we practice to deceive!” Sir Walter Scott Let’s look and some misinformation – or is it disinformation? – that is commonly reported. Misinformation – erroneous information that is passed on through ignorance. Disinformation – deliberate lies or distortions used to promote one’s cause or agenda.
OXYMORON – “TRUE” R VALUE Fiberglass industry only reports R value of batt insulation that is: – Perfectly placed – No studs, fasteners, wiring, etc. – No stapled facings – Batts must be in contact with all surfaces – Never happens in the field – FALSE R values reported – True R values MUCH lower
OXYMORON – “TRUE” R VALUE Wood industry reports R value of batts, not the wall assembly. – Does not include heat flow through studs – Ignores air gaps from imperfect placement. Stapled facings leave gaps Wiring leaves gaps – False R values reported – True R values MUCH lower
MASONRY – TRUE R VALUE NCMA – Calculates or tests true R value of wall assembly – Only reports True R values – Notes the effects of mass in reducing heat flow, but only as recognized by ASHRAE and supported by analysis.
Those “R” Lies Lie #1 – ICF walls have an R value of 50 – Some say “Equivalent R Value of 50.” – Equivalent to what? Truth – Typical ICF walls are R16 to R20
Those “R” Lies Lie #2 – 6” Steel stud walls are R 19 – Steel stud conducts much heat through the wall – R19 batts are only R19 if perfectly placed with no gaps Truth – 6” steel stud walls have typical R 7.03 according to AHSRAE 90.1
Those “R” Lies Lie #3 – 6” Wood stud walls are R19 – Wood studs conduct less heat than metal studs – Wood studs conduct more heat than insulation – R19 batts are only R19 if perfectly placed with no gaps Truth – typical 5.25” wood stud walls are R11.4 or less
Those “R” Lies Lie #4 – 4” Wood stud walls are R13 – Wood studs conduct more heat through the wall than insulation – R13 batts are only R13 if perfectly placed with no gaps Truth – perfectly built 3.5” wood stud walls actually R 8.4. Truth – many 3.5” wood stud walls R5 or less
Detailed Look at Wall Systems Now let’s look at these wall systems in more detail and calculate their actual R value using the ASHRAE series-parallel method: When DIFFERENT wall components are in the SAME LAYER, we add the heat flows (U values) for each component in that layer. (PARALLEL) – Accounts for thermal bridging that bypasses insulation. – R for that layer = 1/(Sum of U values) When wall components are in SEPARATE LAYERS, simply ADD the R values. (SERIES) Here are examples of walls designed for true R19
A. True U and R Values in Building Walls In this session we will compare each of the following wall systems. Each has peculiar advantages that can make them appropriate choices, but it is important to understand their limitations. 1.Wood Stud Walls 2.Steel Stud Walls 3.Insulated Concrete Form Walls 4.Tilt-up Concrete Walls 5.Single-Wythe Masonry Walls 6.Masonry Cavity Walls
1. Wall Systems – Wood Stud AdvantagesDisadvantages Moderate cost Ease of routing wiring and other utilities Fire destroys it Water damage – mold and rot Air and moisture barriers REQUIRED to prevent damage Air leaks cause poor energy performance Thermal bridging cause poor thermal performance
1. Wall Model – 4” Wood Studs Calculate actual R value Series/parallel method R 3.5 – wood stud U x 15% = R 13.0 – batt R 9.1 reduced 30% for imperfect fill U x 85% = U Total = = R = 7.33 average stud cavity R = x 0.625” gyp board R = 8.4 average opaque wall
1. Wall Model – 4” Wood Studs Calculate actual R value Series/parallel method R 3.5 – wood stud U x 15% = R 12.6 – spray foam, sprayed cellulose, or aminoplast foam filled U x 85% = U Total = = R = 9.05 studs and insulation layer R = x 0.625” gyp board R = 10.2 total when stud cavities are filled with insulation, no gaps
1. Wall Model – 4” Wood Studs Calculate actual R value Series/parallel method R 3.5 – wood stud U x 15% = R 16 –aminoplast foam filled U x 85% = U Total = = 0.96 R = 10.4 studs and insulation layer R = x 0.625” gyp board layer R = 11.5 total when stud cavities are filled with insulation, no gaps
1. Wall– 6” Wood Studs Calculate actual R value Series/parallel method R 5.5 – wood stud U x 15% = R 17.4 – compressed R 19 batt R 12.2 reduced 30% for imperfect fill U x 85% = U Total = = R = 10.3 average stud cavity R = x 0.625” gyp board R = 11.4 average opaque wall
1. R19 Wall – 4” Wood Studs R 0.33 – Masonry veneer R 1.0 – Air space R 10.0 – 2” XPS insulation R 8.4 – Wood Studs with R 13 batts* R 0.17 – outside air boundary layer R 0.68 – inside air boundary layer R 20.6 – Total 10.4 inches total wall thickness
1. R19 Wall – 6” Wood Studs R 0.3 – Masonry veneer R 1.0 – Air space R 5.0 – 1” XPS insulation R 10.3 – Wood Studs with R 19 batts* R 0.17 – outside air boundary layer R 0.68 – inside air boundary layer R 19.5 – Total 11.9 inches total wall thickness
2. Wall Systems – Steel Studs AdvantagesDisadvantages Moderate cost Ease of routing wiring and other utilities Noncombustible Subject to water damage – rust and mold Air and moisture barriers required to prevent damage Air leaks cause poor energy performance Batt insulation less effective, cannot be well placed
2. R19 Wall– 6” Steel Studs R 0.3 – Masonry veneer R 1.0 – Air space R 10.0 – Continuous insulation R 7.03 – Steel studs with R 19 batt (ASHRAE Handbook of Fundamentals) R 0.17 – outside air boundary layer R 0.68 – inside air boundary layer R 19.1 – Total 12.9 inches total wall thickness
3. Wall Systems – Insulated Concrete Form AdvantagesDisadvantages R15 to R19 insulation built in Strong reinforced concrete core Low air infiltration STC50+ sound barrier Combustible forms must be protected by fire barriers both sides Mass of concrete is isolated from building interior Thicker walls reduce floor space Toxic gases in fires Blowouts and other construction issues
3. R19 Wall– Insulated Concrete Form a R 0.3 – 3” Masonry veneer R 1.0 – 1” Air space R 9.5 – 2.5” EPS insulation form R 0.48 – Concrete pour R 7.5 – 2.5” EPS insulation form reduced by electrical cut-outs R 0.4 – ½” gyp board R 0.68 – inside air boundary layer R 19.4 – Total R 0.17 – outside air boundary layer 15.3 inches total wall thickness
4. Wall Systems – Tilt-up Concrete AdvantagesDisadvantages Some general contractors have carpenters as permanent employees to build forms 24’ tall 6” walls Hard concrete surfaces require low maintenance Very durable Not damaged by water Low air infiltration Very high strength Non-combustible and very fire resistant STC 50 sound barrier 100 Year Life Limited insulation Continuous insulation it cavity wall is only way to reach prescriptive R values in energy code Limited finishes and profiles Higher cost Utilities must be in place and slab poured before walls can be cast Heavy cranes required More space required onsite Level site required
4. R19 Wall – 6” Tilt-up Concrete R 0.5 – 6” Tilt-up Concrete Negative side dampproof coating R 10.0 – Continuous insulation (Seldom used – R10.3 without ci) R 9.0 – 6”x25ga Steel studs, R 19 batts (ASHRAE Handbook of Fundamentals) R 0.17 – outside air boundary layer R 0.68 – inside air boundary layer R 20.3 – Total 15.6 inches total wall thickness
4. R19 Tilt-up Concrete Sandwich Panel R 0.2 – 2” Concrete R 14.0 – Continuous insulation 2” polyisocyanurate R 0.17 – outside air boundary layer R 0.68 – inside air boundary layer R 15.6 – Total 10.0 inches total wall thickness R 0.5 – 6” Concrete
5. Wall Systems – Single-Wythe CMU AdvantagesDisadvantages Very Low cost 24’ tall 8” walls Hard masonry surfaces require low maintenance Very durable Not damaged by water Low air infiltration Very high strength Non-combustible and very fire resistant STC 50 sound barrier 100 Year Life Limited insulation capacity limits use in some climate zones More difficult to run wiring
5. Wall Model – Single-wythe CMU R 5.7 – Core insulated CMU with grouted cells at 32” minimum and bond beams at 48” min spacing (per IECC prescriptive tables) R 0.68 – inside air boundary layer R 6.55 – Total R 0.17 – outside air boundary layer 7.63 inches total wall thickness
6. Wall Systems – Masonry Cavity Wall AdvantagesDisadvantages Moderate cost Unlimited insulation Hard masonry surfaces require low maintenance Very durable Not damaged by water Low air infiltration Very high strength Non-combustible and very fire resistant STC60+sound barrier 100+ Year Life Slightly higher cost
6. R19 Masonry Cavity Walls a R 0.3 – 3” Masonry veneer R 2.5 – Foil-faced 1” air space R 14 – 2” foil-faced polyiso board R 2 – 6” CMU uninsulated R 0.68 – inside air boundary layer R 19.5 – Total R 0.17 – outside air boundary layer 11.3” inches total wall thickness
6. Wall Model – Masonry Cavity Walls a R 0.30 – Masonry veneer R 2.5 – Foil-faced 1” air space R 10.5 – 1.5” foil-faced polyiso board R 5.7 – 8” CMU grouted 48” c/c R 0.68 – inside air boundary layer R 19.9 – Total R 0.17 – outside air boundary layer 12.8 inches total wall thickness
Summary: R values, Thickness and Cost R ValueThickness$ / sq ft 1a. 4” Wood Studs with Brick VeneerR ” 1b. 6” Wood Studs with Brick VeneerR ” 2. 6” Steel Studs with Brick VeneerR ” 3. Insulated Concrete Form with Brick VeneerR ” 4. Tilt-up Concrete with Insulated StudsR ” 5. 8” Single-wythe CMU WallR ” 6a. 6” CMU Masonry Cavity Wall with Brick VeneerR ” 6b. 8” CMU Masonry Cavity Wall with Brick VeneerR ” Notes: 1.Every wall system in this list requires continuous insulation to achieve R19. 2.Consider aesthetics. Most of the above do not have finished masonry inside and out. 3.Consider durability. Masonry and concrete will last indefinitely. 4.Consider maintenance. Masonry and concrete surfaces require very little maintenance. 5.Consider Life Cycle Cost, not just first cost. 6.Consider fire resistance. Wood buildings burn to the ground in 20 minutes or less. 7.Finally consider overall value. Masonry cavity walls give most for your money.
True Mass Effect Many wall systems, including masonry, tilt-up, and ICF’s claim a benefit from mass in the wall system to improve energy performance. Computer simulations at ORNL show where mass should be placed for maximum benefit. This debunks claims of some wall systems to benefit from mass.
Oak Ridge National Laboratory Study This recent study at ORNL found significant improvement in energy performance of a 1500 sf house with properly placed mass elements in the walls.
HDD / CDD 4” EPS3” Conc 4” EPS2” Conc4” Conc4” EPS6” Conc 4” EPS3” EPS2” EPS 1” EPS WALL 1WALL 2WALL 3WALL 4WALL 5WALL 6 MASS INSIDE INSULATION OUTSIDE MASS OUTSIDE INSULATION INSIDE (TILT-UP WITH INSIDE INSULATION) MASS NOT EFFECTIVE MASS BURIED IN INSULATION (ICF) MASS NOT EFFECTIVE
ORNL Study – Energy Use in Houses
Cavity Wall Savings Table 4 - Annual Cooling Energy Demand (Mbtu /Yr) CDD=> WallATLDNVRMIAMINNPHXWADC %-56.5%-3.2%-31.6%-5.2%-26.5% Table 5 - Annual Heating Energy Demand (Mbtu /Yr) HDD=> WallATLDNVRMIAMINNPHXWADC %-3.0%-16.7%-0.8%-28.8%-2.2% Table 5 - Annual Heating and Cooling Energy Demand (Mbtu /Yr) WallATLDNVRMIAMINNPHXWADC %-5.2%-3.3%-1.6%-8.5%-4.8% -30%-21%-13%-6%-34%-19% Similar to Masonry Cavity Wall ICF Wall Cavity Wall Savings Savings on heat flow through wall only (estimated)
What does this mean? 1.This study shows significant savings for walls with mass exposed to inside air compared with mass isolated within insulation. 2.Walls account for only 25% of the heat loss for these houses. 3.If we divide total savings in heat load by 25%, we can see that walls with mass exposed to inside air reduce heat loss through walls by up to 34% in Phoenix and 30% in Atlanta. 4.DFW savings would be in this 30% range as well.
Limitations on the ORNL study. 1.Significant wall types were not studied: a.Masonry veneer over steel studs b.Masonry veneer over wood studs 2.Whole building energy modeling does not show heat losses in walls directly
NBS 45 Study July 1973 Computer models Full scale testing Showed mass benefits – Stabilized indoor temperatures – Reduced heating and cooling loads +/- 0.8° F indoors ° F outdoors
Proposed Mass House in DFW Using the adobe effect in DFW, a mass house could greatly reduce energy consumption by storing several days’ heat flow to take advantage of outside temperature variations and eliminate mechanical heating and cooling. Walls would be solid masonry or concrete to maximize mass. Ground floor would be slab-on-grade with perimeter insulation to maximize heat storage in the slab and the soil under it with ground temperature at 68ᵒF. Attic floor would be 8” solid concrete. Total mass for 1500 sf house would be 600,000 lbm At 0.22 sp heat it takes 132,000 btu to raise the temperature one degree F. In 18 hours of 90 deg weather, temperature will rise 3 deg F
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2011 Daily High and Low Temperatures, DFW Airport Daily Highs Daily Lows Thermostat Set-points 68ᵒF to 75ᵒF Efficient Air Conditioning Ventilation Only No Heat or AC Solar Heating
Daily high and low temperatures in the DFW area shows approximately 6 months when outside temperatures fall within the comfort zone as defined by thermostat set points. During these times, outside air could be brought in to either heat or cool indoor air at appropriate times of the day. Light-framed houses will require supplemental heating and cooling during these times, because they can only store sufficient heat to maintain temperatures for several hours. Proposed Mass House in DFW
Mass houses can store enough heat to maintain comfortable temperatures for several days. With proper ventilation programming, mechanical heating will be required for only 2.5 months in winter. This can be easily provided by solar collectors, which can also supply domestic hot water. So far we have net zero energy, except for fans, lighting, and plug loads. Cooling will be required for about 3.5 months in summer. But mass storage allows running cooling system when outside temperatures are at their lowest. This decreases total energy use for cooling by 25% and shifts energy loads to off-peak hours to allow better use of alternative energy sources, such as wind power. Proposed Mass House in DFW
Mass houses can store enough heat to maintain comfortable temperatures for several days. Heating and cooling minimized in spring and fall weather Long cooling cycles maximize cooling efficiency Off-peak heating and cooling – Better use of alternative energy sources – Much lower energy costs with electric discounts Mass House in Any Climate
Comparing Wall Systems Summary and Conclusions True R values differ widely among wall systems Masonry cavity walls can match any level of insulation Tilt-up has limited insulation capacity, unless an insulated cavity and masonry veneer is added. ICF has limited insulation capacity that is adequate, but not better than masonry cavity walls. ICF walls are 4”thicker than masonry cavity walls for the same insulation value. Masonry cavity walls cost less than either ICF or tilt-up walls.
Comparing Wall Systems Summary and Conclusions Steel and wood framed walls have very limited insulation capacity without added cavity insulation. Steel and wood framed walls often have moisture damage from corrosion and mold. Tilt-up panels with inside insulation have very limited insulation capacity and also can have moisture damage from corrosion and mold.
Comparing Wall Systems Summary and Conclusions Masonry cavity walls are by far the most versatile wall systems: – Widest range of insulation capacities – Strong aesthetic qualities – Moderate cost – 8” modules work at a human scale – Speed of construction – No cranes or heavy equipment required – Few site limitations – Disaster resistant – fire, flood, wind, seismic – Carries structural loads with ease
eQUEST & Simergy Energy Modeling User-friendly shell for whole building energy analysis, especially Simergy. Complies with IECC energy codes ASHRAE 90.1 or IECC compliance paths User selects building size, shape, and envelope and mechanical elements with few limits. Change walls, windows, and other envelope components to compare performance. Free! Developed by Lawrence Berkley Labs – Download at DOE website.
eQUEST & Simergy Energy Modeling Demonstrates compliance with IECC where prescriptive methods fail. Single wythe CMU walls comply in Climate zones 1 – 6. Much lower cost buildings to meet or exceed energy codes.
Enjoy your eQUEST ! And may your life overflow with Simegy! Enjoy your eQUEST ! And may your life overflow with Simegy! John E. Swink, PE, LEED-AP Acme Brick Company 801 Airport Freeway Euless, TX Cell
Kentucky School Energy Study The following slides are used by permission from a PCMA presentation by Dr. W Mark McGinley, from a recent study directed by him at University of Louisville. Complete report can be obtained from the author by request.