Masonry Magazine June 1987 Page. 31
Simple payback is the cost of a measure divided by its first year savings; thus, $1200/$193.14 is equal to 6.2 years. If discounted payback or life cycle costing methods were employed, more rapid return on investment would be demonstrated. Builders generally consider options with less than 7 years simple paybacks to be quite "Cost Effective."
General Insulation Guidelines
The R-Value zones shown on The National Map in Figure I are generally cost effective for concrete masonry full basements under the following criteria: a) using national average energy prices at a 4.5% per year escalation rate; b) using energy conservation cost data from the NAHB-Research Foundation (Draft) report to the ASHRAE 90.2P Standards Committee; and c) a spot check using the Parker version of the F-Factor method which is based on the same heat loss model as that used to prepare data for ASHRAE 90.2P.
Using the map as a starting point, local insulation costs and energy prices should be investigated to determine locally most cost effective options for basement insulation. In all cases the application of values shown on the map should provide reasonable life-cycle cost effectiveness for heated basements.
Figure 2 contains examples of typical concrete block basement wall insulation systems in use today. Selection from these popular approaches should satisfy any of the thermal protection levels identified in Figure 1.
Figure 2(a) shows a CMU wall with full exterior extruded polystyrene insulation (R-5 per inch).
Figure 2(b) illustrates a fully pre-insulated masonry wall, or wall with insulating inserts. By selection of specific types of insulated block, nearly any level up to R-12 can be obtained.
Figure 2(c) shows a block wall fully filled with loose-fill or foamed-in-place insulation. A wide range of R-Values can be obtained using various products.
Figure 2(d) illustrates use of "skirts" of insulation typically either 2 feet or 4 feet down the wall. This approach is generally not as effective as full wall insulation, but may be effective in some areas.
Figure 2(e) is a case where the designer selects some specific number of courses of pre-insulated block to reduce heat loss at or near the soil surface. This approach and that shown in 2(d) are generally used only in more mild climate regions.
Figure 2(f) shows how insulated block and various exterior rigid board insulation panels can be combined to meet especially severe insulation requirements while still providing interior architectural appeal.
Other basic basement construction guidelines are:
■Fully parge and waterproof block walls prior to installing exterior insulation.
■Be sure adhesives and waterproofing agents are compatible with plastic insulation.
■Caulk and seal all utility openings in the foundation wall thoroughly
■Provide gravel and a 6 to 8 mil poly vapor retarder underneath slab
■Floor slabs should use a perimeter thermal break which doubles as an expansion joint
■Consider use of pre-insulated block with architectural facings on the interior face
Provide adequate ventilation, natural light (at least 2% of floor area should be in windows) and heating of the area for best comfort
■Consider passive solar heat collection using "walk-out" patio doors
Figure | General Recommendations for Concrete Masonry Basement Wall Insulation on Exterior or Using Pre-Insulated C/M Units
(Number in Parenthesis Indicates Wall Coverage From Top of Basement Wall)
NR Denotes No Requirement
*Local Microclimates May Permit Use of R-10(8')