Rough Code so far... Was able to get it to verify in the arduino IDE. I had a photo sensor tutorial in my arduino starter kit and was able to piece together part of the circuit. Right now i have another test sketch which turns on an LED to indicate day or night as proof of concept.

I also added in some logic to check if the relay is already on before switching it on, and to make sure it is on before switching it off so i am not constantly looping and telling it to shut off when already off. Not sure if this is necessary but i wanted to be on the safe side so i don't burn anything out.

Will probably be a week or so before i get the rest of the parts i need (relays and temp/humidity sensor).

Questions / Need help with:

- Should i totally isolate the relays from the arduino (by feeding them a separate power source) as described below?

NOTES: 
If you want complete optical isolation, connect "Vcc" to Arduino +5 volts but do NOT connect Arduino Ground.  
Remove the Vcc to JD-Vcc jumper. 
Connect a separate +5 supply to "JD-Vcc" and board Gnd. 
This will supply power to the transistor drivers and relay coils. 

Work In Progress Mockup:

CODE:

/*-----( Import needed libraries )-----*/
#include "DHT.h"

/*-----( Declare Constants )-----*/
#define RELAY_ON 0
#define RELAY_OFF 1

/*-----( Declare Variables )-----*/
#define DHTPIN 2     // what pin we're connected to for DHT22
#define Relay_1  3  // Arduino Digital I/O pin number for first outlet
#define Relay_2  4 // Arduino Digital I/O pin number for second outlet
#define DHTTYPE DHT22   // DHT 22  (AM2302)

DHT dht(DHTPIN, DHTTYPE); // Initialize DHT sensor for normal 16mhz Arduino

// Connect pin 1 (on the left) of the sensor to +5V
// NOTE: If using a board with 3.3V logic like an Arduino Due connect pin 1
// to 3.3V instead of 5V!
// Connect pin 2 of the sensor to whatever your DHTPIN is
// Connect pin 4 (on the right) of the sensor to GROUND
// Connect a 10K resistor from pin 2 (data) to pin 1 (power) of the sensor

int lightPin = 0; //the analog pin the photoresistor is connected to
                  //the photoresistor is not calibrated to any units so
                  //this is simply a raw sensor value (relative light)

int ledPin = 9;   //Night Indicator LED
int ledPin2 = 10; //Day Indicator LED

int threshold = 700; //Photosensor value for Night time
int lightVal = 0; //Variable to hold reading from photosensor
boolean nightInd = false; //True/False to indicate if day or night. True = Night time

//HUMIDITY THRESHOLDS
float dayRHthresholdUpper = 60.00; //DAY RH High threshold when exhaust is turned on
float dayRHthresholdLower = 40.00; //DAY RH Low threshold when exhaust is turned off

float nightRHthresholdUpper = 60.00; //NIGHT RH High threshold when exhaust is turned on
float nightRHthresholdLower = 40.00; //NIGHT RH Low threshold when exhaust is turned off

//TEMP THRESHOLDS
float dayTempThresholdUpper = 78.00; //DAY Temp High threshold when heat is turned off
float dayTempThresholdLower = 75.00; //DAY Temp Low threshold when heat is turned on

float nightTempThresholdUpper = 70.00; //NIGHT Temp High threshold when heat is turned off
float nightTempThresholdLower = 66.00; //NIGHT Temp Low threshold when heat is turned on


void setup()   /****** SETUP: RUNS ONCE ******/
{
//-------( Initialize Pins so relays are inactive at reset)----
  digitalWrite(Relay_1, RELAY_OFF);
  digitalWrite(Relay_2, RELAY_OFF);
  
//---( THEN set pins as outputs )----  
  pinMode(Relay_1, OUTPUT); //Humidity outlet (exhaust fan - do not exceed 1200watts)
  pinMode(Relay_2, OUTPUT); //Heat outlet (heater - do not exceed 1200watts)   
  delay(4000); //Check that all relays are inactive at Reset

  pinMode(ledPin, OUTPUT); //Night Indicator LED
  pinMode(ledPin2, OUTPUT); //Day Indicator LED

  Serial.begin(9600); //start up serial output
  dht.begin(); //assuming this turns on the DHT22 sensor

}//--(end setup )---




void loop()   /****** LOOP: RUNS CONSTANTLY ******/
{
  lightVal = analogRead(lightPin);  //Read photosensor value
  
  delay(2000);  // Wait a few seconds between measurements. DHT22 is slow.
               // Reading temperature or humidity takes about 250 milliseconds!
               // Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
  

  float h = dht.readHumidity();  // Read Humidity
  float t = dht.readTemperature();  // Read temperature as Celsius
  float f = dht.readTemperature(true);  // Read temperature as Fahrenheit
  
  // Check if any reads failed and exit early (to try again).
  if (isnan(h) || isnan(t) || isnan(f)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }
  
  
  if(analogRead(lightPin) > threshold){   //This is NIGHT TIME
   digitalWrite(ledPin, HIGH); //Turn night indicator LED ON.
   digitalWrite(ledPin2, LOW); //Turn day indicator LED OFF.
   nightInd = true;
     }else{  //This is DAY TIME
       digitalWrite(ledPin2, HIGH); //Turn day indicator LED ON.
       digitalWrite(ledPin, LOW); //Turn night indicator LED OFF.
       nightInd = false;
     }

  
  
  //------DAY TIME------//
  if (nightInd == false){  //nightInd = false so this means it is daytime
  
  // If humidity hits threshold, turn on exhaust (outlet #1)
  if (h > dayRHthresholdUpper) {
      if (Relay_1 == 1){  //Make sure relay is not already on before switching
    digitalWrite(Relay_1, RELAY_ON);// set the Relay ON
  delay(1000);              // wait for a second
      }
  }
  // If humidity hits threshold, turn off exhaust (outlet #1)
  if (h < dayRHthresholdLower) {
      if (Relay_1 == 0){  //Make sure relay is on before switching off, else do nothing since its already off
      digitalWrite(Relay_1, RELAY_OFF);// set the Relay OFF
  delay(1000);              // wait for a second
      }
  }
    // If temperature hits threshold, turn heat on. (outlet #2) 
  if (f < dayTempThresholdLower) {
            if (Relay_2 == 1){  //Make sure relay is not already on before switching
        digitalWrite(Relay_2, RELAY_ON);// set the Relay ON
  delay(1000);              // wait for a second
            }
  }
  // If temperature hits threshold, turn heat off. (outlet #2) 
  if (f > dayTempThresholdUpper) {
            if (Relay_1 == 0){  //Make sure relay is on before switching off, else do nothing since its already off
        digitalWrite(Relay_2, RELAY_OFF);// set the Relay OFF
  delay(1000);              // wait for a second
            }
  }
  }//------END DAY TIME-----//



  //------NIGHT TIME------//
  if (nightInd == true){    
  
  // If humidity hits threshold, turn on exhaust (outlet #1)
  if (h > nightRHthresholdUpper) {
    if (Relay_1 == 1){  //Make sure relay is not already on before switching
    digitalWrite(Relay_1, RELAY_ON);// set the Relay ON
  delay(1000);              // wait for a second
    }
  }
  // If humidity hits threshold, turn off exhaust (outlet #1)
  if (h < nightRHthresholdLower) {
        if (Relay_1 == 0){  //Make sure relay is on before switching off, else do nothing since its already off
      digitalWrite(Relay_1, RELAY_OFF);// set the Relay OFF
  delay(1000);              // wait for a second
        }
  }
  // If temperature hits threshold, turn heat on. (outlet #2) 
  if (f < nightTempThresholdLower) {
        if (Relay_2 == 1){  //Make sure relay is not already on before switching
        digitalWrite(Relay_2, RELAY_ON);// set the Relay ON
  delay(1000);              // wait for a second
        }
  }
  // If temperature hits threshold, turn heat off. (outlet #2) 
  if (f > nightTempThresholdUpper) {
        if (Relay_2 == 0){  //Make sure relay is on before switching off, else do nothing since its already off
        digitalWrite(Relay_2, RELAY_OFF);// set the Relay OFF
  delay(1000);              // wait for a second
        }
  }
  
  }//------END NIGHT TIME-----//


  float hi = dht.computeHeatIndex(f, h);  // Compute heat index, might be useful later...
                                          //Must send in temp in Fahrenheit!
                    
                    
  //DEBUG Outputs
  Serial.println(lightVal); //Photosensor value
  Serial.println(nightInd); // True = Night | False = Day
  Serial.print("Humidity: "); 
  Serial.print(h);
  Serial.print(" %\t");
  Serial.print("Temperature: "); 
  Serial.print(t);
  Serial.print(" *C ");
  Serial.print(f);
  Serial.print(" *F\t");
  Serial.print("Heat index: ");
  Serial.print(hi);
  Serial.println(" *F");

}//--(end main loop )---