Energy Efficiency in Residential

Structures

By

Matthew Wynne

The Future is NOW

IECC 2015Ceilings R49

Walls R20 or R13 + R5 continuous

Floors R19

Windows U 0.35 / SHGC 0.40

Foundation R10 cont. or R13 cavity

Duct Leakage 4 CFM per 100sf

Loads, sizing ACCA Manual J,S

Shell Leakage 3 ACH 50

ECCCNYS 2014Ceilings R49

Walls R20 or R13+R5 continuous

Floors R19

Windows U 0.32 / SHGC 0.40

Foundation R15 cont / R19 cavity

Duct Leakage < 4 CFM per 100sf

Loads, sizing ACCA Manual J,S

Shell Leakage < 5 ACH 50

International Energy Conservation Code

and

Energy Conservation Construction Code of New York State

Home Energy Rating System

Most municipalities in LI require a HERS rating for new construction

Plans review

Before construction, it must be determined whether the building as

designed can pass the rating. HERS raters use REM/Rate software to

calculate the projected rating.

Air sealing inspection

Site visit to verify that proper shell-sealing techniques are used

Insulation inspection

Site visit to verify that insulation has been installed correctly

HERS Rating

HERS Rating

• Combustion analysis

- Check fuel-fired appliances for proper draft and CO

• Gas leakage test- Check exposed gas pipe couplings for leaks with a gas detector

• Worst-case depressurization

- Close doors and run pressure drivers (fans, dryer, AHUs, etc) to see if draft and CO in

natural-draft space- and water-heating appliances are affected

HERS Rating

Blower door test

• Measures air leakage through the building shell by

depressurizing the building

• Measures in Cubic Feet per Minute under 50

Pascals of pressure (CFM 50)

• 1 Pascal = 0.004 inches of water column

• Simple to covert to Air Changes per Hour under 50

Pascals (ACH 50)

• 5 ACH 50 equivalent to around 1/3 ACH natural

HERS Rating

Duct blaster test• Measures air leakage to outside from duct systems

• Previous standard was 6 cfm per 100sf

• New standard is 4 cfm (very tight)

• Ducts and AHU seams must be sealed with mastic

• HVAC in attic?

Insulation - Fiberglass• Can be blown-in (usually attics, settles over time)

• R3.1 – 3.8 per inch

• Batts – most common

• Compression and voids lower R-value

• Should touch all sides of cavity

• Must be face-stapled, not side-stapled

• Not the best choice for basements

Insulation - cellulose• R3.2 – R3.7 per inch

• Modern cellulose made from recycled paper

• Can be blown-in wet (walls) or dry (attic floor)

• Better than batts at filling voids

• Dry-blown settles over time

Insulation - Spray Polyurethane FoamPros:

• Cures quickly (if mixed/applied correctly)

• No lingering odor (if mixed/applied correctly)

• Vapor and air barrier, makes for a tight house

• ~R3.7 per inch – open cell (or low density)

• ~R6 per inch – closed cell (or high density)

• Walls, ceilings/roofs, foundations, sills/rims

Insulation - Spray Polyurethane FoamCons:• Expensive

• Cures poorly (if mixed/applied incorrectly)

• Long-term off-gassing (if mixed/applied incorrectly)

• Very difficult to remove

• Many shingle manufacturers require vented roof assembly

• Roof leak could cause extensive rot to sheathing before it’s discovered

• Look for: Cracks, visible sheathing, color inconsistency

Insulation – foam boardsEPS – Expanded polystyrene – R4 per inch (white)

XPS – Extruded polystyrene – R5 per inch (green, pink, blue)

Polyisocyanurate – R7 per inch (yellow, with foil faces)

• Waterproof, mold-proof

• Provides thermal break for framing

• Air/vapor barrier if seams taped

Snow on roofs

What can be gleaned from these roofs?

Optimum Value Engineering

• a/k/a Advanced framing

• Eliminates unnecessary lumber

• Reduces framing factor from 25% to 15%

• Many builders / code enforcement officials unfamiliar

Windows• “Weakest link” in the thermal boundary

• Window upgrades for energy efficiency

only is not a good investment

• NFRC sticker

• U-factor is reciprocal of R-value (1/R),

i.e., U 0.30 = R 3.33

• Solar Heat Gain Coefficient (SHGC)

considered in cooling loads

• Low-E (low emissivity) coatings

• Argon gas fill

• Triple glazings

Windows• Aluminum frames allow more thermal

transmission than vinyl or wood

• Aluminum frames used in high-rises to

resist wind loads

• Rubber spacers replace aluminum

ones and provide more of a thermal

break

• Casement windows are most draft

resistant

• Older window performance can be

improved with storms or drapes

Air-sealing

Attic plane (top ceiling)

• Hi-hats

• Scuttle / pulldown

• Plumbing vents

• Chimneys

• Chases

• Top plates

• HVAC in attic

Common leak points

The biggest offender for energy losses

Air-sealingAttic plane (top ceiling)

Ice dams

• Heating cables treat symptoms, not cause

• Cause treated by improving air sealing and

insulation

Air-sealingSill plates / rim joists

Heating Efficiency

Different types• Annual Fuel Utilization Efficiency (AFUE)

~ output / input, i.e., 100KBtu input, 85KBtu output = 85% AFUE

• Combustion efficiency- calculated by determining oxygen, stack temperature, draft, CO, CO2

• Distribution efficiency- leaky ducts or uninsulated pipes in unconditioned spaces = transmission losses

• Building loads- insulation, window quality, shell leakage, weather

HVAC – condensing furnace / boiler• Up to 98% AFUE

• Modulation – changeable firing rate

• Gas (LP or NG) only

• Not available for steam

• Direct intake / exhaust – no vent in room

• Polypropylene exhaust (230°F)

• Exterior intake must face down

• Exterior exhaust – avoid snow blockage and frozen condensate; side termination should be pitched back to unit

• Insect screens, usually ¼-inch mesh

• Condensate neutralizer

• Wall-hung boilers

• Steel or aluminum heat exchanger

• Life span 15 – 30 years

HVAC – Steam• Best around 85% AFUE

• Steam vents – should be on mains and main

risers

• Steam vents should not hiss and not be

painted

• Near-boiler piping should be insulated

• Clean old boiler internals and adjust pressure

• Stack damper and auto-ignition (gas only)

• Near-boiler piping should be sized according

to manufacturer

HVAC – mini-splits• Inverter technology

• Super-efficient – up to 21 SEER

• Variable speed fan / variable flow refrigerant

• Heat pumps can work down to 5ºF or 10ºF

• No ducts (or duct leakage)

• Very quiet

• Up to 4 heads per condenser

• Good for retrofits where ducts

would be difficult

• As sole heat source should still have

aux heat

Domestic hot waterIndirect-fired storage tanks

• No separate burner to maintain

• Efficiency pegged to boiler

• Life span comparable to

standalone unit (10 – 15 yrs)

Domestic hot waterOn-demand (tankless)• No standby losses

• Gas or electric

• Comparable efficiency decreases with elevated hot water

usage

• Sized to 90º temperature rise for ? GPM

• Takes longer for hot water to arrive, i.e. wastes cold water

• Should be flushed regularly

• Life span 10 – 20 years

Domestic hot waterHeat pump water heater

• Uses air-source heat pump to heat water (reverse of refrigerator)

• Good choice when electrical is the only option

• 2x – 4x cost of electric resistance unit

• Can be up to 2.5x more efficient than resistance coil units

• Side effect: space cooling and dehumidification

• Can be exhausted to exterior, but equal volume of outside air

will enter the building

• Operating range usually 40ºF - 90ºF

• Performance based upon room temperature (warmer is better)

• Room should be minimum of 1000 cubic feet or performance

may suffer

• They typically have resistance coil backup

• They drip, like an air conditioner

• Tend to be loud, like a wall A/C

• Too new for reliable life span track record

Domestic hot waterCombination units

• Heat and DHW in one

unit

• Similar features to

condensing boilers and on-

demand water heaters

Domestic hot waterDHW Circulator

Domestic hot waterDHW Circulator

• Larger houses and small apartment buildings

• Pump activated by timer or motion sensor

Mechanical ventilation• Required in tight houses (<= 5 ACH 50 or <= .35 ACH natural)

• Calculated as per ASHRAE 62.2

• Exhaust only: Bathroom fans with programmed timers

• Supply only: Rare in houses, would connect to HVAC return duct

• These types can be unbalanced, which means pressure differences

between inside and outside.

• Pressure differences can lead to IAQ issues and condensation

inside wall / ceiling assemblies

Mechanical ventilationHeating Recovery Ventilator (HRV)

• Balanced Airflow (intake and exhaust fans)

• Recovers heating/cooling by up to 75%

• Exterior ports should be at least 10’ apart

• Exterior air intake should be away from pollution sources such as: plumbing

vents, chimneys, dryer vents, traffic, garbage, etc.

• System should ideally be independent of HVAC ducts, or interlocked

• Interior ports: one should draw, one should blow, should be on opposite sides

of the building for best results

• Interior air intake (to exhaust) can draw from bathrooms / kitchen unless ERV

is used.

• Ducts should be installed well and insulated

• Maintain regularly with other HVAC equipment

• Energy Recovery Ventilator transfers latent energy (moisture) as well as heat

Mechanical ventilationHeating Recovery Ventilator (HRV)

Resources

• Web sites

- buildingscience.com

- bpi.org

• Book

- Residential Energy by Krigger / Dorsi