As Colorado builders who design and construct custom homes on your lot, RKM Homes sees ventilation as a performance feature, not an afterthought. Modern high‑performance homes in and around Denver are built tight to meet energy goals and reduce drafts, which means stale indoor air, moisture and pollutants can build up if there’s no controlled ventilation. An ERV, or energy recovery ventilator, provides a continuous, balanced supply of fresh outdoor air while exhausting the same volume of indoor air—recovering the thermal energy and some moisture between the two airstreams so you don’t lose the heating or cooling you paid for.
An ERV moves two air streams through a core where heat and latent energy are transferred from the warmer stream to the cooler one. In winter that means incoming cold air is pre‑warmed and slightly humidified by the outgoing indoor air; in summer the incoming hot, humid air is pre‑cooled and dehumidified. Because the system exchanges air in equal volumes it avoids pressurization issues that can draw soil gases into the home, and built‑in filtration removes large particulates and pollen before air reaches living spaces. ERVs can be ducted into a central HVAC system or installed as a dedicated unit with feeds to key rooms; proper sizing and balanced airflow are essential for effective operation.
For homeowners the practical benefits are tangible: lower indoor concentrations of CO2, VOCs, cooking and cleaning fumes, and reduced allergy triggers thanks to pre‑filtration and constant fresh air—while keeping heating and cooling costs lower than using uncompensated ventilation. In Denver’s dry winters an ERV helps retain comfortable indoor humidity; in shoulder seasons it provides fresh air without overworking your furnace or A/C. At RKM Homes we specify and commission ERVs to match occupancy, layout and local climate, and recommend routine filter changes and annual checks so the system continues to protect indoor air quality and energy performance for the life of the home.
Is an ERV or HRV better for my Denver home and how will it affect humidity control?
In Denver’s high‑altitude, semi‑arid climate—cold, dry winters and warm summers with occasional moisture events—ERVs (energy recovery ventilators) are often the more practical choice. Unlike HRVs, which only exchange sensible heat, an ERV transfers both heat and moisture between incoming and outgoing air. That means in winter an ERV will reclaim some of the indoor moisture and help prevent the home from becoming excessively dry when outdoor air is brought in, and in summer it can help limit the humidity load brought into the house during humid periods. From a builder’s perspective, that steady humidity moderation reduces cracking in wood finishes, helps preserve engineered floors and cabinetry, and improves perceived comfort without oversizing auxiliary humidification.
That said, selection should be based on real project conditions and occupant needs. If you expect to run a whole‑house humidifier or dehumidifier independently, or the house will be virtually unoccupied for long stretches, an HRV can still be acceptable. For most occupied custom homes in Denver we specify ERVs with proven latent transfer efficiency—look for cores with measurable moisture transfer (typical effective latent performance is often in the 40–70% range) and reliable cold‑weather defrost strategies. Units with a summer bypass or variable fan speeds give you practical control: bypass for cool, dry spring nights; active moisture recovery during winter; and higher flow when you need fast dilution after cooking or parties.
Practical next steps for homeowners: measure your current indoor relative humidity through a seasonal cycle (aim for roughly 30–45% in winter, 40–60% in summer), tell your builder or HVAC contractor those targets, and insist the ventilation design consider both ASHRAE 62.2 ventilation rates and moisture behavior. Specify an ERV with a humidistat or integrated controls, variable speeds, accessible filters for routine cleaning, and a defrost strategy suited to cold Colorado winters. Finally, plan system commissioning: balance the flows, verify humidity performance during the coldest and warmest days, and add supplemental humidification or dehumidification only if the ERV alone can’t meet your comfort and preservation goals.
What size ERV do I need and what ventilation rates are required by code?
Start by calculating the minimum continuous ventilation rate most jurisdictions reference from ASHRAE 62.2: Ventilation CFM = 0.03 × conditioned floor area (ft²) + 7.5 × (number of bedrooms + 1). That formula gives the continuous CFM an ERV needs to provide to meet occupant and building-area requirements; if you plan to run ventilation intermittently, the required peak CFM must be increased to achieve the same long‑term air exchange. Local codes sometimes adopt ASHRAE directly or modify the numbers, so have your conditioned square footage and bedroom count ready when you talk to your builder or permitting office.
When selecting the unit, size the ERV to meet that calculated continuous CFM at realistic duct static pressures — not just the manufacturer’s free‑air rating. Specify an ERV with multi‑speed or variable‑speed fans so it can run continuously at the low design rate and be boosted for parties, painting, or heavy cooking. Account for pressure drops from filters, grilles and any in‑line dampers: a unit that delivers 150 CFM in the spec sheet might only deliver 120 CFM after ducts and filters are added, so choose a model with some capacity margin and check rated performance at 0.2–0.5″ w.g. external static pressure.
On practical jobs I produce a ventilation worksheet for the owner and include the calculated CFM on the plans so the ERV and ductwork are sized in permitting and bidding. After installation, commission the system with airflow measurements (flow hood or certified technician) and balance supply vs. exhaust within about 10% so the house stays near neutral pressure. Request controls that allow continuous low speed plus a manual or automatic boost mode, and confirm the installer documents the final CFM and control settings in the owner’s operation manual so you can maintain the IAQ performance over time.
How should an ERV be integrated with my HVAC system, ductwork layout, and building envelope?
Place the ERV where it can share short, direct duct runs with the central air handler—typically the mechanical room, a conditioned attic space, or a finished basement mechanical closet. Co-locating minimizes additional static pressure and keeps runs short, which preserves fan capacity and reduces noise. The best practice is to create dedicated supply and exhaust branches from the ERV (not just a loose tap into the supply plenum) with properly sized, insulated ductwork and manual balancing dampers. Avoid long runs of flexible duct; use smooth metal ducts for main trunks and keep elbows to a minimum. Mount the unit on vibration isolators and leave at least the manufacturer’s recommended service clearances so filters and cores can be removed without squeezing past piping or electrical panels.
A tight building envelope changes how the ERV must be set up: because the unit intentionally brings makeup air in and expels indoor air out, the intake and exhaust terminations must be carefully located and sealed through the envelope to prevent backdraft, moisture intrusion, or contamination. Make sure termination points are separated from any combustion vents, dryer vents, or roof valleys, and that penetration details are flashed and sealed like any other exterior penetration. Coordinate ERV exhaust and local exhaust fans (kitchen, bath) so the house isn’t pushed excessively positive or negative; that coordination is done with dampers, controls, and commissioning rather than by guesswork. For cold climates, confirm the ERV has freeze protection or a drain/defrost strategy and that condensate lines slope to a proper drain.
When you’re contracting a custom home, require the ERV to be fully integrated on the mechanical drawings and specified for serviceability and controls: specify minimum filter MERV, accessible filter access, condensate drain connection, electrical disconnect, and clearances. Ask the builder or MEP to show the proposed duct layout, anticipated static pressure, and where the ERV control will be mounted (on the HVAC thermostat, a dedicated wall control, or via building automation). Insist on post-install commissioning—measured CFM, measured pressure balance, and a noise check in living areas—plus a simple maintenance schedule (filter type and replacement interval) written into the homeowner turnover packet.
How often should I change ERV filters, what filters should I use, and how do I make service access easy?
As a custom home builder I specify ERV filtration knowing homeowners want clean air without constant hassle. Choose a pre-filter in the MERV 6–8 range for routine dust and construction debris; it catches large particles without creating excessive pressure drop. If you or your family have allergies or wildfire smoke concerns, plan for a secondary filter slot that can accept a higher-MERV (9–13) panel or a dedicated HVAC-grade filter, but only after confirming the ERV’s allowable pressure drop so the fan can still move the required air. Also confirm whether the ERV uses a washable enthalpy core or a disposable core — washable cores need a different cleaning cadence and access than replaceable cartridges.
When I lay out mechanical spaces I design for serviceability first: place the ERV so the filter face and core are reachable from the front with at least 30 inches of clear working space, provide a hinged access panel and removable frame for filters, and label each filter slot with size and change interval. Make sure the intake and exhaust grilles have insect screens and are reachable for seasonal checks; include a simple condensate drain access if the model has one. Insist the unit be mounted so the core can be removed straight out without disconnecting ducts — that saves homeowners time and prevents accidental duct damage during servicing.
Expect a predictable maintenance rhythm: inspect pre-filters monthly for the first three months after moving in, then every 1–3 months depending on dust, pets, and wildfire smoke; replace disposable pre-filters when visibly loaded. Plan to clean or replace the ERV core annually (more often if you live near ash-producing fires or heavy construction). Schedule a professional check every 1–3 years to verify motor bearings, damper operation, and condensate drains; if you notice reduced airflow, stale odors, or increased dust, check filters immediately rather than waiting for the next service interval.
How energy-efficient is an ERV, what will it cost to run, and are there incentives or control options I should specify for my home?
As a custom home builder in Denver, I tell clients that modern residential ERVs use very little electrical power compared with the energy they recover. Typical continuous fan power for quality units is often in the 20–60 watt range; at 30 W continuous that’s about 263 kWh per year (0.03 kW × 24 × 365), which at $0.15/kWh is roughly $40/year in fan energy. Because an ERV transfers heat and some moisture between incoming and outgoing air, it can recover 60–80% of the ventilation-related heating or cooling energy in many climates, so the recovered energy usually more than offsets the small fan cost. When you’re vetting equipment, ask for the unit’s measured sensible/enthalpy recovery efficiency and its rated power draw at the design airflow so you can compare apples-to-apples.
Check available incentives and build them into your budget and spec package before ordering. Many local utilities and state programs offer rebates for high-efficiency ventilation or whole-house energy improvements; some federal programs have credits that may apply depending on installation and energy modeling results. We always request preliminary rebate eligibility letters as part of the mechanical submittal and provide the manufacturer spec sheet and performance test data the utility will want. Don’t forget operating costs beyond electricity: include filter replacement frequency and cost in your lifecycle estimate and require the installer to document expected annual service tasks.
Controls make the difference between an ERV that’s efficient on paper and one that actually saves you money and improves air quality. Specify an ERV with an ECM/variable-speed motor and a control package that supports timed boost, occupancy/CO2 or humidity-based demand control, and a thermostat/air handler interlock so the ERV can ramp up when the HVAC fan runs rather than fighting it. For practical commissioning, require the contractor to set a continuous low-speed baseline per ASHRAE ventilation rates, program boost modes for cooking and bathing, and leave a simple homeowner interface or app with clear run-time and filter-change reminders.