Incorporating Building Performance Into New Construction: A Checklist

07/20/2004

 Don Michael Jones, Residential Building Analysis

Introduction

This checklist was developed by Don Michael Jones, a valued and skilled trainer at many ACI Conferences. It was based on his personal experience and summarized or adapted from the Energy and Environmental Building Associations (EEBA) Builder’s Guide: Cold Climate, 2002 Edition by Joseph Lstiburek and Betsy Pettit of the Building Science Corporation. This book and the others in the series provide a very detailed and fully illustrated resource for builders and architects on practical building science applications. (See Resource List at end).

Assure Moisture Control for the House

Foundation:

• Provide a granular capillary break and drainage pad under the entire slab foundation.
• Install a capillary break/vapor barrier across the entire area where the foundation and slab contact the footer and the sub-slab fill. This is most easily accomplished by using 6 mil polyethylene sheeting. In the case of the footer to foundation wall capillary break, a dampproofing material can be substituted for the plastic membrane.
• Install an effective dampproofing material on the below grade foundation walls of both basement and crawlspaces.
• Depending on the soil type, install perforated drainage pipes around the foundation base and tie them into an appropriate drainage and/or sump pit system.
• Install perforated drainage pipes in the sub-slab fill material and tie into a temporarily capped T joint that terminates above the basement/crawlspace slab. This will allow for the later installation of a sub-slab depressurization system if it is needed to isolate the house from moisture or other soil gasses.
• If a sump pit is located in the basement or crawlspace, install a sealed cover to isolate the foundation drainage and its moisture from the house. Floor drains should be one-way so that the drain is closed off from the air of the house when not used.

Drain Planes and Flashings:

• Install a flashing style lapped drain plane (building paper or air infiltration barrier) material over the wall sheathing material.
  • Masonry and wood siding materials should have a drainage/drying space between the sheathing material and the interior surface of the siding.
  • Masonry unit sidings should be installed in a way that any water entering the space can drain out at the bottom.
  • Wood sidings should be applied over batten strips and painted/sealed on all four sides.
• Proper flashing details should be provided for any roof to roof and roof to wall intersects.
• Proper flashing details should be provided to protect the window and door framing from water drainage where the drain plane intersects the window frame.

Note: These steps are most critical in cold, damp climates and warm, damp climates. Cold, dry climates allow trapped moisture to dry out more quickly.

 

Assure Consistent Insulation Coverage

• Install loose-fill insulation over the floors of all open joist style attics. If the ceiling is a low-pitched “faux” vaulted ceiling, staple a retaining material (i.e. cardboard or fan fold foam) along the edges to retain the blown material.
• Install the same insulation level all the way out over the top plate and protect from any low ventilation air (soffit mounted vents).
• Protect the insulation in closed rafter cavities (i.e. cathedral ceilings) from the intrusion of ventilation air by installing edge-sealed vent chutes or some other air barrier material to maintain an isolated air channel above the insulation and below the roof deck.
• On any vertical surfaces exposed to the air of an attic space, use a high-density insulation form (cellulose damp spray or behind mesh) or cover the insulation with a sealed air barrier material (spun olefin membrane, rigid insulation board, duct board, plywood, etc.)
• Damp spray cellulose can be installed to a high density in the above grade exterior walls. Due to its installation density (more than 3 lb/cubic ft.), this form of insulation has a higher degree of resistance to air leakage intrusion. It also performs at a higher level without a taped/sealed exterior air barrier required by the lower density batt forms of insulation.
• If batt insulation is used, fit it tightly between the framing and snuggly against the heated surfaces with no gaps, puckers or channels that will allow conduction and air-flow to degrade the insulation performance. If a kraft-backed vapor barrier form is used, the fastening flange should be stapled to the inside edge of the framing. This includes both exterior surfaces (walls, cathedral ceilings, cantilevers) and surfaces bordering buffered spaces (attic floors, floors over garage spaces, kneewalls).
• Insulate floors above unheated spaces, garages, bay windows, and especially cantilevers, to the full capacity of the framing with a tightly air sealed blocker at each edge (interior and exterior) of the floor space.
• Install foundation insulation so that it covers the entire height of the wall, especially when it is hollow core concrete block. Always insulate the surfaces that are above grade.
  • Interior Application: Insulation forms that are moisture resistant (Expanded or Extruded Polystyrene) should be used when placed against the inside of the foundation masonry material. Isolate the wood or metal framing/furring of the finish wall material from the masonry to provide both a thermal and a capillary break.
  • Integral Application: Foam insulation can be installed into the cores of the concrete masonry units from the top plate down to the footer.
  • Exterior Application: Rigid board insulation or insulated drainage board can be installed below grade down to the footer with foam insulation installed into the cores of the concrete units in the above grade portion of the wall.

 

Assure a Complete Air Barrier Across the Building Shell

• Air-seal the joints and openings in either the drywall or the sub-siding in order to assure the performance of the wall insulation.
• Insulate and air-seal the first and second story rim joists. Air sealing the perimeter of a floor truss system is very, very, very important.
• Insulate and air seal cantilevers. Block them off from the remainder of the floor joist cavities where they intersect the plate. Avoid placing supply registers in the cantilever if it is possible. If a duct is inside the cantilever cavity, make sure the insulation fills around that duct and that the interior edge of the cavity is tightly sealed.
• Complete an air barrier across the surfaces bordering all buffered areas (attics, crawlspaces, garages) that are intended to be outside the conditioned space. It is critical to close off and air seal all framing that opens between the unconditioned and conditioned spaces of the house.
• Avoid or at least minimize the use of recessed lights. Use sealed can recessed light fixtures (IC) and seal the gap between the can and the drywall.
• Close and seal any interior partition wall framing cavity openings between the attics and heated spaces. It is especially important to cap and seal the edges of any mechanical chaseways, horizontal framing from ceiling height changes, and drop soffits above cabinets, tubs, vanities, etc.
• Seal all mechanical penetrations through the attic ceiling, rim joists into the floor cavities, garage walls, and basement walls/floors with appropriate materials being careful to attend to the temperature and moisture requirements of the area to be sealed. Chimneys, flues, plumbing stacks, light fixtures, exhaust fans, ducts, wiring, refrigerant lines, floor drains and sump crocks all need to be appropriately sealed.
• Carefully air seal smaller attic spaces (bay windows, breakfast nooks, sun rooms, etc) away from the floor/ceiling joist cavities of the main house. The gap left where the joist hangers are attached to the support beam hold the drywall away from the framing (1/8-1/4”) can be a significant air leakage bypass between the “attic” spaces and the 1 st/2 nd story joist cavities
• For the maximum draft proofing effect on the structure, mechanical system and other types of building shell penetrations should be sealed at the exit point. In other words, the most cost effective approach to sealing a two story tall thermal bypass is to seal it where it penetrates into the attic not where it opens into the basement.

Assure Effective Heating and Cooling Delivery

• Install the highest efficiency heating and cooling equipment that is economically feasible. It is important to remember that the highest efficiency heating equipment, 90% efficient furnaces and high performance heat pumps, tend to distribute lower temperature air than traditional furnaces. As such, they do not have the capacity to overcome ineffective insulation and uncontrolled drafts. It is important to have a tightly sealed and insulated building shell if a high efficiency heating system is used.
• Avoid the use of atmospheric draft appliances in houses. Sealed combustion or fan induced draft appliances are preferable. The draft of an atmospheric appliance is a relatively weak pressure and as such can be overcome by negative pressures created by the comparatively stronger mechanical fans (bathroom fans, dryers, down draft kitchen fans, etc) that are found in many homes.
• Assure the proper sizing of the mechanical equipment intended to heat and cool a house. Building shells that are air sealed and insulated to MEC 95, IECC 2000 or higher standards (EPA ENERGY STAR®) often require smaller BTU capacity than has been traditionally installed in a given size house. Over sizing air conditioning can be especially detrimental to both efficiency and the comfort delivered by the system. It’s critical to perform Manual J (see Resource List) or other sizing calculations to determine the most appropriate system to match the energy features of the house.
• Avoid providing too much supply air to the basement or house-connected crawlspaces. This condition can lower the overall static pressure of the system and reduce airflow to other areas of the house creating comfort problems. The supply and return plenums should be carefully sealed with a mastic or other acceptable sealant and plenum or trunk mounted registers should be avoided.
• Supply registers for the basement should be attached to ducts taken off of the trunk in the same manner as the ducts for the upper floor. The majority of basements, if air sealed and well insulated, will be comfortably heated with the radiant loss off the furnace plenum/ducts and a couple of well placed supply registers. Air conditioning is seldom required in the basement and as such, the registers should be closeable.
• Avoid running ducts outside the conditioned spaces whenever possible.
• Avoid using framing systems as a part of the return side of the distribution system. If you use the framing, it needs to be isolated and sealed away from unconditioned areas (especially attics and garages).
• Thoroughly air-seal all ducts that are located outside of the heated space with mastic or other acceptable sealant (not duct tape).
• Bury any ducts located in the attic under additional insulation. Install the loosefill insulation over the ducts to as close to the ceiling insulation level as possible.

 

Consider Alternative Framing Strategies to Improve Thermal Performance

• Change framing corners from a 4 stud, solid wood corner, to a 3 stud or even 2 stud corner, which will allow you to install insulation within that framing corner. (See section on “Optimal Value Framing” in the EEBA Builders Guide as cited on Resource List).
• Use a ladder style interior partition wall catcher so that full insulation can be installed between the juncture of the interior and exterior walls. Air seal interior partition walls away from the exterior wall cavities.
• Use rigid insulation instead of plywood as the spacer for window and door headers (R3-R4).
• Use a raised heel truss or a raised rafter plate to allow for a full R-30+ across the ceiling out to the top plate.
• Use a scissor style truss whenever possible to create vaulted ceilings rather than attaching the ceiling directly to the rafters. This will allow for a higher level of insulation and will help avoid the adverse effect of ventilation air flowing through the ceiling insulation.

 

Consider Alternative Interior/Exterior Finishes

Additional ways to improve thermal performance and moisture control

• Construct true cathedral ceilings (drywall on rafter) without roof venting. This is called a hot roof assembly and involves air sealing the drywall thoroughly, completely filling the rafter cavity with insulation, and installing plywood over the rafters, a layer of rigid foam insulation on top of that layer and then the roof deck material over the foam. A less expensive alternative would be to put the foam directly on the rafters and then cover with the plywood. Some code regulations may not allow this approach.
• Extend the exterior wall and ceiling drywall behind and above the interior partition walls in order to better seal them away from the outside or buffered spaces such as attics.
• Use the Airtight drywall approach (gasketed/sealed drywall) to provide a tight interior air barrier especially if a low -density wall insulation form is used.
• Provide a perm rating of 1 or less by applying sufficient primer and finish paint layers rather than applying a polyethylene vapor barrier or kraft paper insulation batt behind the exterior wall drywall. Damp spray cellulose should not have a polyethylene vapor barrier installed across the interior surfaces of the walls.
• Use taped or sealed spun olefin or building paper over the sheathing as a combination air infiltration barrier and drainage plane.

 

Author Background

Don Michael Jones was Principal of Residential Building Analysis in Columbus, Ohio. His practical knowledge of home construction techniques and focused presentation style made him a popular and effective trainer at ACI conferences. His untimely death in 2004 was a tremendous loss to his family, his colleagues, and the home performance industry. In honor of his memory, a scholarship fund has been established to help new building practitioners, particularly students, attend ACI trainings. For more details, check the ACI website at www.affordablecomfort.org.

 

Resource List

EEBA Builders Guide: Cold Climates…Joe Lstiburek and Betsy Pettit, EEBA, Minneapolis, MN, Website: www.eeba.org. More discussion and illustrated details are found in this guide and the others in the series.Building Science Corporation:www.buildingscience.com .

Manual J - Residential Load Calculation, 8th edition…Air Conditioning Contractors of America, Arlington, VA, Website: http://www.acca.org/ .

Disclaimer: ACI, Inc. does not endorse any specific products or services. Opinions expressed herein are those of the author and do not necessarily reflect the opinions of ACI, Inc., although they have been reviewed and considered to reflect the industry perspective at the time of publication.

© ACI, Inc., July 2004