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Building Science and Foundation Design Principles

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Introduction to Building Science and Envelopes

Building Science, Envelopes (BED), Small Large Simple Complex. Design details envelope, building (skin), Environment Control (Separation of physical environment, int/ext, int/int). History: After WWII began Ottawa National Research Council, Canada Leading. Building Systems: Architectural (e.g. wall cladding, masonry), Structural (holds it up), Mechanical (HVAC, plumbing, drainage), Electrical (lighting systems, power), Landscaping.

Practitioners (Building Sciences) often Engineers (structural, environmental), architects or Technologists, Consultants (acoustics, roofing, conservation, environment). Building Science Corp (Forensics).

Building Science Principles and Envelope Design

Building Enclosure; Enclosure Typologies: Monolithic Enclosure (load-bearing masonry - single material, structure, cladding, int. finish, control heat, air, moisture), Composite Assembly (control heat transfer or air leakage to support materials), Structures (Stacked units, frames, shells, plates, air supported fabrics). Cladding/Interior Finishes: wet coatings, discrete units or panels, fabrics, films, sheets, rolls.

Limit States Design: Environmental Loads (rain, temp, humidity, int climate states decay, mold, corrosion). Redundancy & Multi-Functionality: Moisture Migration (Bulk water; shading, conveyance, drying, storage, drying, drain screen, perfect barrier, Capillary Water; Barrier/Break, Vapour Diffusion; V.B., thermal insulation, Air Leakage; A.B. System, thermal insulation). Heat Transfer (Conduction; thermal insulation, Radiation; R.B., Convection; A.B. System). Air Leakage (Stack, wind, mech effects - A.B. System). Solar Radiation (Heat; orientation, fenestration, shading devices, thermal resistance, glazing reflectance, emissivity, Visible Light: same before, glazing optical properties).

Problems Associated with Building Envelopes

  • Deterioration: due to moisture penetration, air leakage. Lead to mold, mildew, wetness.
  • Energy Consumption: Poor energy conservation increases costs.
  • Occupant Health/Comfort: Provide healthy environment, Sick Building Syndrome.
  • Operation of Mechanical Systems: Balancing HVAC systems, depends on tightness of building envelope.
  • Indoor Air Quality / Indoor Environmental Air Quality: Tightness of envelope prevents pollutants escaping inside/outside.
  • Hypersensitivity to Construction Materials.

Types of Construction

Commercial/Residential. Different materials & methods / contractors. Commercial (Part 3, Building Code, Industrial/Institutional). Residential (Part 9, Building Code, Small wood construction).

Environment Control

Building envelope control of 8 physical factors, separation of environments, control flow, movement, transfer of physical elements.

Major Physical Factors

  1. Heat Transfer: Conduction - molecules in solid excited by heat source applied to an object; Convection - occurs in fluids H2O or Glycol or Gas Materials; Radiation - Heat transfer from warm to cool object giving off heat waves; Air Leakage - holes ext wall force liquid and gas through opposite temp on either side of wall (push/pull); Measured in Joules/BTU.
  2. Moisture Penetration (Solid, Liquid, Gas): 4 sources - precipitation, ground water, condensation (concealed - inside wall, surface condensation), occupants. 3 simultaneous conditions occur: Source - moisture, Opening - hole/crack, Force. 5 Driving Forces Moisture: Moisture Penetration Forces - Gravity (runs down surface building), Surface Tension (water sticks to surface/introduce drip), Capillary Action (suction - anything less 3mm = effect drinking straw / make joint bigger / low pressure inside to high pressure outside), Momentum (Kinetic Energy - wind driven / put in baffle), Air Pressure Differential (moisture control air pressure / water goes to lowest pressure / add pressure equalized chamber / air chamber). Water penetration measured in volume & time (L/Sec, g/min).
  3. Vapour Diffusion: Gaseous state of water, go through wall both ways - uniformly - slow weak physical force - other gases carbon monoxide, radon. Tyvek permeable to vapor diffusion (water proof not vapor proof). Glass non-permeable (good). Vapour Diffusion Forces: WVPD - Water Vapour Pressure Differential States - lots of water vapour pressure goes higher to lower pressure. Air Leakage - not static goes in-out simultaneously. Metric Measured - weight (nano g), Imperial - (PSI).
  4. Air Movement: Leads to Air Leakage, Still Air = very high thermal resistance - good insulation, moves high-low pressure areas, APD - air pressure differential, Building pressurized (corridor to rooms) or depressurized (room pulls) measured K-pascals. 3 Forces: Stack effect (major force drives air movement in building, hot air rise sucks cold air, low pressure down by floor (neutral pressure plane) convection loop, Infiltration at bottom/exfiltration at top, high air pressure = top, low = bottom); Wind Pressure (Windward side - blow on wall outside, Leewrd - blow inside, Wind pressure in-out, Positive side/Negative side); Mechanical Pressure (fan pressure [flue & ventilation effect], chimney suck low pressure upwards - sucks inside air, HVAC, Air Condition). Measured in Volume, time & area (L/Sec/m^2 at 50-75 Pascals).

Minor Physical Factors

  1. Fire (Fire Protection): flame/heat, steam/smoke, gases (most dangerous), fire separations or fire walls, FRR: Fire Resistant Rating (Measured in time), control flow, movement, spread & transfer.
  2. Sound, Sound Control: sound barrier (party wall between units), control sound transfer by absorption, deflection, bounce. Sound easily pass through less dense materials (concrete, gypsum). Insulation helps absorb/control sound. Measured in dB.
  3. Radiation: light, solar heat energy, nuclear radiation, Solar heat energy; heat gain/loss (radiant heat), Passive Solar Heat Gain - free heating of sun, UV radiation damage to construction materials.
  4. Environmental Impact: Sustainability - energy efficiency, embodied energy (cons. materials), recycling, dipolar; Pollution - solid (dust effecting respiratory systems), liquid (SO2, sulphur dioxide mixing with water in air = acid rain), Gas (carbon monoxide). Heating/Cooling. Carbon Footprint.

Building Envelope Components

  • Foundations: foundation wall sit on footing, slab on grade, piles (poor soil conditions), 2 parts - wall below earth and above.
  • Floors: Ground floor, Typical floor, Slab on grade, Header - floor meets ext wall.
  • Walls: Int/Ext walls, structure - substructure - cladding - finishes. Walls (party wall), part 5 OBC, separation spaces, environmentally dissimilar int spaces.
  • Roof: supports ext from int (horizontal wall), 1st line of defence, ext wall meets roof (comm - parapet wall, res - eave).
  • Openings: reinstate continuity of building, eg - windows, doors, skylights, roof hatches, mech/elect penetrations in foundation needs to be sealed properly, moisture tight, air tight.

Building Envelope Deterioration Mechanisms

  • Structural: vibration will shake building apart, impact, air pressure (material/structural fatigue), settlement, concrete creep (bow slab to level out over time), basic structures must be robust enough to resist physical forces, earthquake.
  • Hydro-Thermal: Freeze thaw cycle - damage brick, thermal expansion/extraction (need strong joints), moisture penetration.
  • Electro-Chemical: Oxidant (rust), Galvanic action (diff metals touch bad), EMR - Electric Magnetic Radiation.
  • Bio-Chemical: mold, mildew, fungus, decay/rot, acid rain, insects (termites, carpenter ants), animals.

Building Environmental Design Directives

  1. Building Type (Typology): typical building, heat moves from hot-cold, non-typical building - different flow, hot-cold reversed usually (arenas, computer rooms, pools) thermal expansion/contraction, hot to cold.
  2. Direction Movement: infiltration (moves from ext to int), exfiltration (out-in) of physical factors (transfer at different times).
  3. Rate Movement: speed of movement, wind pressure or air leakage, air conditioning temp drop takes a long time. Speed fast to slow - slow to fast.
  4. Panels, Joints, Junctions (Concept): building env composed many materials & conditions. Panel: Large area of sm material, Joint: connection of same materials (control joint connect - brick = similar), Junction: connection or intersection of dissimilar materials (brick meets metal or glass wall), Dynamics; moves easier, thermal expntn.
  5. Environment Barriers: thermal barrier (insl), moisture barrier (WRB), V. Barr (warm sd of thermal barr), Air. Barr (self adhesv flexbl mmbrne), Sound Barr (prty wall), Fire Barr (alum foil bckd wth plstc), Env. Barr / Pollutn. Barr > Physical Factors acting on building env, control through series of barriers.
  6. Building Movement: thermal expansion & contraction, joints & materials, wind/pressure, settlement - foundation, cracks, vibration HVAC, structural change, earthquakes.
  7. Tolerances: construction dirty business.
  8. Redundancy: 2nd line of defence - details will fail plan ahead.
  9. Durability: last over time.
  10. Repairability
  11. Environmental Impact: construction materials & methods.
  12. Economics: cost/quality.
  13. Aesthetics
  14. Climate: micro/macro.

Cladding Principles

Types of Cladding Systems

  1. Face Seal Construction: least sophisticated, least expensive, simple principle, cladding on & seal ext system, only 1 line of defence.
  2. Drained System (Concealed Barrier, Drainage Cavity): moisture will get into wall thus drainage system in wall (drainage plane) Tyvek, Building paper, flexible membrane materials (blu.skin), moisture barriers, req flashing & weepers at btm of detail for water to get out.
  3. Cavity (Rain Screen System): takes care of wind driven rain, momentum, doesnt take care of air pressure differential, min width 10mm to max 50mm (common 19mm), allows for +drainage/+ventilation, needs moisture resistant materials in drainage cavity, req flashing & weepers every 3rd brick horizontally, cavity goes from back of panel to VP, Air space: back of panel to insl, except mineral insl allows air pass thru.
  4. Pressure Equalized / Moderated Wind Screen (PER Wall): air pressure inside cavity = air pressure outside cavity, moisture leakage will not occur. 3 Main Components: Rain Screen (cladding - brick, steel siding, stone, precast conc siding), Air Chamber (same as air cavity), Air. Barr (pressure equalization occurs) must be supported & rigid in both directions.

Types of Cladding Components

  • Wind Distribution: leeward side - neg pressure, windward side - wind is coming from, wind pressure, wind distribution.
  • P.E.R. Wall "compartmentalization".
  • Ventilation: must be sufficient size to allow for instantaneous air pressure equalization, vent size calculated by measuring air leakage (LxW) - blower door test: x by 20, put in that many vents & weepers & will get PER WALL, Weepers at bottom & vents at top (avoid convective air chamber).
  • Compartmentalization: wind pressure on building not uniform (dynamic) higher up higher pressure, wind pressure can change miraculously, air pressure can move laterally & vertically, physically separate air chambers (especially up the corners across parapet & down other side.

Wind Pressure at Corners

Compartmentalization, P.E.R. Wall Drying, Backer Rod - supporting 2 chambers - crammed in 2 corner, Galvanized Metal Air Dam - continuous all the way down, Rigid Insl (XPS Foam) - continuous all the way down, Shelf Angles, Openings (Windows & Doors); Two-Stg Joint.

PERSIST

Pressure Equalized Rain Screen Insulation Structure Technique (insulation outside structure, panels-joints-junctions do not use 1 stage joint).

Moisture Management Strategies

  1. Deflection: deflect rain, overhang, there will be low & high exposure planes, cornices there to protect wall with zero overhang or cornice, 90% water problem were reported, so 600mm wide overhang 25% water problems occurred/reported.
  2. Drainage (Can.Wood.Concl.Mstr.Mgmt.Strtds): Drainage: create cavity, drainage plane, gravity, through wall with weeper.
  3. Drying: drying occurs evaporation & diffusion into interior & exterior.
  4. Durable Materials: use pressure treated sils or water resistive materials.
  5. Storage: store moisture in wall seasonally, doesnt apply to modern arch.
  6. Exclusion: water tight material (glass), use water vapour impermeable materials, hard to achieve with joints, panels, junctions.

Types of Wall Systems

O.A.A. Rain Control Strategy Wall System: mass wall storage - concrete wall has certain amount of room to store water, will store it until sun dries it out; Exclusion: perfect barrier - no moisture in wall (glass & metal curtain wall). Res & Comm. Wall Systems.

Building Facade Wetting Pattern

Buildings get wet near top & top edges (water on windward side). Exposure Level (2 Moisture): if hilly site lots of wind.

Foundations Introduction

Important, holds building up, transfer load to earth. Soil Conditions: Solid Rock - granite (good for foundation, costly to remove); Softer Rock: limestone, shale, sand, silt (minor particles), clay (loose) (Leda clay + water = BAD). Geotechnical Survey.

Foundation Components

Footing, Foundation Wall, Slab, Pile Foundations (Generally used for comm., large buildings or used for bad soil conditions).

Foundation Types

  • Pile Driver: drill (generally made of wide flange steel columns, sometimes made of concrete or pressure treated wood).
  • End Bearing Pile: drive it or drill it into ground to point of refusal (friction).
  • Caisson Pile: big steel pipe, could be 1-2m in diameter (reinforced bars - poured concrete).
  • Raft Foundation: for large buildings (wet sites - floats on wet soil).
  • Augured Pile Foundations: commonly for decks.

3 Basic Types of Foundations

  1. Full Basement: Footing below frost line, gravel site is drain free.
  2. Slab on Grade (SOG): no basement, must protect against frost heave, cheaper. 2 Types: SOG with conventional foundation wall, SOG with grade beam.
  3. Crawl Space: manage rain & ground water (slop away from house). 2 Types: Unconditioned Crawl Space (corrodes materials, certain codes dont allow it anymore, well ventilated space, airtight floor assembly, apply rigid impermeable insl on underside of floor structure. Install capillary break at top foundation walls, under floor structure. Install M. Barr. on soil); Conditioned Crawl Space (install moisture bar on soil, use coarse granular fill under slab to provide capillary break, damp proof inside & top crawl space foundation walls, provide floor drain for crawl space area, allow drainage beneath slab, insl on int wall surface must be applied evenly to top of foundation wall above grade. Eliminates mold, corrosion, part of building env).

Foundation Construction Materials & Methods

  • Traditional Materials: stone (cut or dressed stone & rubble stone), cement parging applied to ext (water proofing).
  • Poured Concrete: lots of rebar 200mm, comm. foundation.
  • Masonry: concrete block (commonly used), synthetic stone.
  • P.W.F. (Preserved Wood Foundation): uncommon.
  • Stressed Skin Panels: uncommon - SIP; structural insl panels, foam core, 6mm poly ontop of fresh stone, isolated panels.
  • ICF (Insulated Concrete Framework): made from polystyrene insl - comes in panels, planks, blocks.
  • Pre-Cast Concrete Panels: Built off Site.
  • Shot-Crete: welded wire mesh with insl in middle.
  • Sandwich Panel: full height insl & drainage - concrete on each side of insl, rebar holds it together.
  • Alternative Blocks: Durisol (wood-crete), has insl value but lower than plastic foam (ICF); Drystacked Concrete Block (STACK KING) - dont put mortar joints in it (no insl value); ACC (Autoclaved Cellular Concrete Blocks); E.C.C. (Elect Cond Concrete) - cathodic protection - rebar has current - stops corrosion; High Performance Self Leveling Concrete - developed at NRC - additives make concrete very liquid - advantage for very tight sites.

Major Physical Factors & Foundations

  1. Heat: Materials used in foundations situations (can use outside foundation wall in wet situations). Extruded polystyrene (XPS) R-value 5 per/inch; Mineral Fibre (semi rigid "ROXUL" hydrophobic R-Value 4.3 per/inch (moisture absorption rate .04, thus negligible); Glass Fibre; R-Value 4.2 per/inch "drain clad" (not thermal material when wet); EPS; Expanded Polystyrene (bead board) R-Value 3.6 per/inch. Heat Issues in Foundations: where to put insl; int/ext or combination of both? Thermal Shock; pour concrete - 5yrs still curing (green concrete) susceptible to damage, thermal shock can crack concrete - install ext insl bottom to top of wall, concrete while curing gives off moisture for first 2yrs - dont cover for min 1yr best 2yrs. Should have full height ext insl. Thermal Barrier should go under slab. Synthetic Porging: put on glass fibre mesh hold on by screws & washers, base coat/finish coat.
  2. Moisture: 3 Sources: Ground water, precipitation, condensation. Moisture Issues in Foundations: Drainage Tile - made of high density polystyrene - over top of it geotextile fabric - keeps tiny soils from going thru (sock covered tile, then crushed stone or crushed glass). Drainage Layer: material drains water in soil vertically by gravity through soil. 3 Drainage Layers: (1) AGM - Air Gap Membrane simple in/out, dimples face foundation wall, dimple out, filter cloth on AGM, translucent air gap membrane ideal. (2) Insulation. (3) Granular Fill: crushed stone or post consumer glass. Waterproofing: protects wall from hydrostatic pressure, more expensive, heavy thick membrane, will withstand hydrostatic pressure in soil, rubber wall - coded green - green stuff. Damp Proofing: provides barrier towards damp (water vapour) will not withstand water pressure of the soil (not water proof) - less costly - might as well get 2 coats. Moisture Barrier: inside of foundation wall.
  3. Vapour: control vapour diffusion, gaseous form of water (blue skin outside building is all three: moisture, vapour, heat barrier. Condensation: Surface Condensation; easily dealt with, Concealed Condensation; happens inside thickness of wall - causes mold/fungus inside wall.
  4. Air: air leakage is very powerful physical factor far more important than vapour diffusion, in building envelope component of foundation - air leakage also affects foundation wall, continuous sealant where floor slab meets wall. Materials for Air. Barr: blu skin up above, if water proof membrane applied then air bar created, most commonly used air bar used is concrete, more air bar better, concrete blocks (with parging) are not air tight - must include cement parging create air bar, Precast Concrete Panels: air tight - seal joints, air bar can be placed anywhere in/out wall.

Minor Physical Factors Foundations

  1. Fire: 0%
  2. Sound: 0%
  3. Radiation: 0% below grade - exists above grade - UV radiation above can damage wall (cover with parging).
  4. Environmental: many issues, soil gases, radon gas, radon is radioactive (very bad) must apply soil gasket.

Foundation Design Issues

  • Excavation: site survey; property lines, 4-8, corners of building marked, soil report, contractor surveys it, Excavate site - dig out, Geotechnical: Soil Types, Avoid cave-ins, surveyor locates building footing, formwork, ALL footings must be on undisturbed soil at soil bearing capacity.
  • Shoring: with nearby buildings, excavate vertically keep soil back urban site. Methods: Soldier beams (placed by pile driver), Strong Back (horizontal member), Lagging (wood or steel sheet piling bolted), Tie Backs (if soil very loose).
  • Backfilling: small job - sloped wall bulldozer pushes back into hole, Large jobs - difficult, pile corners 1st.
  • Under Pinning: for free standing buildings & neighbouring buildings, dig down extend foundation wall, can use needle beams, Bench pinning: remove concrete floor slab, excavate existing building, pile of existing earth, step/bench extruding from footing, mud jacking.

Foundation Cracking

Thermal Shock: hot/cold, thermal expansion, winter construction, Back fill pressure. CCM Construction + Material; Poured/mix concrete (scientific) - dont add additional water, Stripping forms - doesnt take formwork off (takes full day usually). Soil Expansion/Contraction - water freezes in soil - cracks footings on foundation wall - settlement over time - drying out of soil (contract) crack - trees soak up moisture. Control Joint Prevents Cracking: holds together weakest point on wall - always put a vertical change - makes wall weak.

Radon

Gas, naturally occurring, soil gas, found in specific areas (rocky sites). Radioactive (health problem for occupants) - prevent with air sealing - eliminate access point. Find where penetration in foundation wall (sub pumps, drainage) - basement must be air tight. Under Slab - crushed stone allows air flow. SPUFF (new): spray polyurethane foam, need full chemical suite, in place of insl or poly vapour barrier under slab.

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