Designs That Work

Very Cold Climate

The Basic House - Energy Analysis Overview

An energy analysis was done for the house plan to examine the energy consumption of the building. With any energy analysis a start point for comparison is required.

The Building America Benchmark Definition Version 2005 along with recent revisions was used as a template for performance evaluation between the advanced building system (Prototype) and the reference building system (Benchmark). The Benchmark Definition requires hourly building energy simulation.

The Building America Benchmark Protocol is generally consistent with mid 1990's house construction. As apposed to other rating performance systems, the Building America Benchmark includes not only heating, cooling and hot water, (which accounts for roughly 50% of total energy consumption of the home), but also energy consumption from lighting, appliances, and other miscellaneous loads.

The following table highlights the differences between the Building America Benchmark House design characteristics and the Prototype design characteristics that were incorporated into this house design.

	Benchmark	Prototype
Building Enclosure	R-21, 16" oc + R-3 Sheathed Walls	R-28 Rigid Foam with Interior Framing
	R-35 Roof Insulation	R-42 Cathedral Ceiling
	Low E Windows (U=0.39, SHGC=0.32)	Low E Windows (U=0.33, SHGC=0.3)
	R-18 Basement Insulation	R-33 Floor on Pier Foundation
	BM Airtightness (~5"/100 sf)	BSC BA Airtightness (2.5 ins/100 sf)
Mechanical	80% AFUE Gas Boiler	Combo System
	R-5 Ducts, 15% Leakage	85% AFUE Hot Water Heater
	0.54 EF Gas Tank Hot Water	Baseboard Heaters
	ASHRAE 62.2 Exhaust Fan	ASHRAE 62.2 Ventilation by HRV
Appliances and Lights	Incandescent Lighting	Fluorescent Lighting
	Regular Appliances	ENERGY STAR Appliances

The simulation program used to run the energy model was EnergyGaugeUSA version 2.42 from the Florida Solar Energy Center.

The areas of consideration fall under three main categories, the Building Enclosure, Mechanical Systems, and Appliances and Lights. A parametric whole house energy analysis was done for the case study house design to illustrate the relative importance of the upgrade strategies in each of the three main areas.

Table 1: Parametric Analysis Results

Note that the estimated cost of change column is a net change, giving credit back for the replaced components. For example, the Benchmark mechanical system includes standard duct installation, standard efficiency heat pump, and hot water heater. Crediting the standard system, the high efficiency system with more air tight ducting and higher efficiency water heater would add $1000 over the cost of the standard equipment.

Figure 4: Total Source Energy Consumption Reduction

The case study model design achieved a whole house 33.1% energy reduction when compared to the Building America Benchmark.

On the basis of BTU/sf/yr of site energy, the above calculations yield the following:

Note that the "Prototype Savings" is source energy savings, whereas the energy use per square foot is site energy, hence the difference in savings.

Figure 4: Building Section


Drainage	Air Barrier

Vapor Management	Thermal Resistance