ZENERGY HOUSE - A Near-Zero Energy Green Healthy Home 
by REAS
ZENERGY Prototype

The Zenergy House project was created by REAS, Inc. as a prototype for "greening" existing homes. The benefits of a High Performance Green Home are improved health, safety, comfort and the ability to protect property values from rapidly escalating energy costs.

ZENERGY HOUSE

  • One Story
  • 2450 sq ft living space
  • 3 bedroom, 3 bath
  • Year Built  - 1950
  • Whole House Remodel
  • Location - Studio City, CA
  • Goal - Near Zero Energy

EE Strategies: Through a comprehensive home energy audit, using a blower door, duct blaster and infrared camera the mechanical systems, building envelope and insulation were diagnostically assessed. 

 
HVAC
The over-sized HVAC system (two 3 ton a/c units & two furnaces) was replaced with a single 3 ton a/c unit and a combined hydronic heating system.  The a/c unit (efficient split system condenser) has a cooling efficiency which is unmatched in the industry       
The inefficient hot water heater was replaced with a high output 99.1% efficient water heating tank connected to a variable speed air handler to serve dual heating purposes.
 
The original ducts had over 20% leakage and were replaced with new ducts that will have no more than 3% leakage, designed for optimum air distribution and installed thru the cleaned and conditioned crawl space. Crawl space vents decrease our energy efficiency by increasing our heating bills in the winter and increasing our cooling bills in the summer.
 
The programmable thermostat automatically adjust temperature settings during the day, evening and weekends to save energy.
 
Insulation
Two small attics were sealed and insulated with encapsulated fiberglass and loose-fill cellulose. Non-toxic 100% silicone and water based caulk were used to properly seal the envelope. The leaky roof was repaired with new underlayment and the existing concrete tiles were reused.
 
Windows                                                                        
All inefficient existing windows and fixed glass block panels were replaced with dual pane, insulated low-e, aluminum clad wood windows.  
 
Lighting
We replaced the old incandescent recessed lights with IC rated sealed CFL only cans and the number of lights were reduced by 30%.  These cans are thermally protected to allow direct contact with insulation and are sealed to eliminate air leaks.  Kitchen under-cabinet lighting and office light fixture use LED bulbs.
 
Appliances
All new appliances are Energy Star qualified. The new bathroom exhaust fans are tied to time sensors so they run only when needed to quietly remove unwanted moisture and odors from the home.  The heat recovery, low sone unit is efficient and good for the homes indoor air quality. Electrical compost installed in the kitchen cabinet uses less than 5 kWh a month and will eliminate waste.  The washer & dryer are among the most efficient currently available on the market.
 
Water
We replaced three existing toilets with high efficiency dual flush toilets with 0.8 & 1.6 gallon per flush that will save up to 40% annually.   Engineered faucets and shower heads are 1.0 and 1.5 GPM and will save not only water but natural gas usage as well. We insulated the hot water pipes and added a circulation pump w/timer on the water heater to eliminate water waste.  The irrigation has a smart sprinkler control system and will save 70% compared to the standard lawn irrigation system that was replaced.  Landscaping includes drought tolerant plants and grasses.
 
Renewable Energy Assessment
The pool is solar heated and does not use any natural gas or additional electricity as it works in partnership with the pool's efficient filter pump.
 
Solar PV (photovoltaic) panels are used to generate electric needs to meet near-zero-energy goals.  A solar array of 12 PV panels  produce 2.4 kWh.  This smaller size system is large enough for the Zenergy House due to the comprehensive efficiency upgrades throughout.

Next to the heating system, a water heater is the largest consumer of energy in the average home. To help choose the correct model, you need to do more than compare prices. Although the cost of a water heater is important, you should consider the hot water requirements, usage patterns and local energy costs. The right mix of these variables will lead to a satisfying purchase.  The gas combination heating in the High Performance Home used a hybrid product that offers the dual performance of both water heating and space heating simultaneously. They are an economical alternative to installing both a heating system and a water heater.